@article{SchmaelzlinMoralejoRutowskaetal.2014, author = {Schmaelzlin, Elmar and Moralejo, Benito and Rutowska, Monika and Monreal-Ibero, Ana and Sandin, Christer and Tarcea, Nicolae and Popp, Juergen and Roth, Martin M.}, title = {Raman imaging with a fiber-coupled multichannel spectrograph}, series = {Sensors}, volume = {14}, journal = {Sensors}, number = {11}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s141121968}, pages = {21968 -- 21980}, year = {2014}, abstract = {Until now, spatially resolved Raman Spectroscopy has required to scan a sample under investigation in a time-consuming step-by-step procedure. Here, we present a technique that allows the capture of an entire Raman image with only one single exposure. The Raman scattering arising from the sample was collected with a fiber-coupled high-performance astronomy spectrograph. The probe head consisting of an array of 20 x 20 multimode fibers was linked to the camera port of a microscope. To demonstrate the high potential of this new concept, Raman images of reference samples were recorded. Entire chemical maps were received without the need for a scanning procedure.}, language = {en} } @phdthesis{Orgis2014, author = {Orgis, Thomas}, title = {Unstetige Galerkin-Diskretisierung niedriger Ordnung in einem atmosph{\"a}rischen Multiskalenmodell}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-70687}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {Die Dynamik der Atmosph{\"a}re der Erde umfasst einen Bereich von mikrophysikalischer Turbulenz {\"u}ber konvektive Prozesse und Wolkenbildung bis zu planetaren Wellenmustern. F{\"u}r Wettervorhersage und zur Betrachtung des Klimas {\"u}ber Jahrzehnte und Jahrhunderte ist diese Gegenstand der Modellierung mit numerischen Verfahren. Mit voranschreitender Entwicklung der Rechentechnik sind Neuentwicklungen der dynamischen Kerne von Klimamodellen, die mit der feiner werdenden Aufl{\"o}sung auch entsprechende Prozesse aufl{\"o}sen k{\"o}nnen, notwendig. Der dynamische Kern eines Modells besteht in der Umsetzung (Diskretisierung) der grundlegenden dynamischen Gleichungen f{\"u}r die Entwicklung von Masse, Energie und Impuls, so dass sie mit Computern numerisch gel{\"o}st werden k{\"o}nnen. Die vorliegende Arbeit untersucht die Eignung eines unstetigen Galerkin-Verfahrens niedriger Ordnung f{\"u}r atmosph{\"a}rische Anwendungen. Diese Eignung f{\"u}r Gleichungen mit Wirkungen von externen Kr{\"a}ften wie Erdanziehungskraft und Corioliskraft ist aus der Theorie nicht selbstverst{\"a}ndlich. Es werden n{\"o}tige Anpassungen beschrieben, die das Verfahren stabilisieren, ohne sogenannte „slope limiter" einzusetzen. F{\"u}r das unmodifizierte Verfahren wird belegt, dass es nicht geeignet ist, atmosph{\"a}rische Gleichgewichte stabil darzustellen. Das entwickelte stabilisierte Modell reproduziert eine Reihe von Standard-Testf{\"a}llen der atmosph{\"a}rischen Dynamik mit Euler- und Flachwassergleichungen in einem weiten Bereich von r{\"a}umlichen und zeitlichen Skalen. Die L{\"o}sung der thermischen Windgleichung entlang der mit den Isobaren identischen charakteristischen Kurven liefert atmosph{\"a}rische Gleichgewichtszust{\"a}nde mit durch vorgegebenem Grundstrom einstellbarer Neigung zu(barotropen und baroklinen)Instabilit{\"a}ten, die f{\"u}r die Entwicklung von Zyklonen wesentlich sind. Im Gegensatz zu fr{\"u}heren Arbeiten sind diese Zust{\"a}nde direkt im z-System(H{\"o}he in Metern)definiert und m{\"u}ssen nicht aus Druckkoordinaten {\"u}bertragen werden.Mit diesen Zust{\"a}nden, sowohl als Referenzzustand, von dem lediglich die Abweichungen numerisch betrachtet werden, und insbesondere auch als Startzustand, der einer kleinen St{\"o}rung unterliegt, werden verschiedene Studien der Simulation von barotroper und barokliner Instabilit{\"a}t durchgef{\"u}hrt. Hervorzuheben ist dabei die durch die Formulierung von Grundstr{\"o}men mit einstellbarer Baroklinit{\"a}t erm{\"o}glichte simulationsgest{\"u}tzte Studie des Grades der baroklinen Instabilit{\"a}t verschiedener Wellenl{\"a}ngen in Abh{\"a}ngigkeit von statischer Stabilit{\"a}t und vertikalem Windgradient als Entsprechung zu Stabilit{\"a}tskarten aus theoretischen Betrachtungen in der Literatur.}, language = {de} } @phdthesis{Herenz2014, author = {Herenz, Peter}, title = {A study of the absorption characteristics of gaseous galaxy halos in the local Universe}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-70513}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {Today, it is well known that galaxies like the Milky Way consist not only of stars but also of gas and dust. The galactic halo, a sphere of gas that surrounds the stellar disk of a galaxy, is especially interesting. It provides a wealth of information about in and outflowing gaseous material towards and away from galaxies and their hierarchical evolution. For the Milky Way, the so-called high-velocity clouds (HVCs), fast moving neutral gas complexes in the halo that can be traced by absorption-line measurements, are believed to play a crucial role in the overall matter cycle in our Galaxy. Over the last decades, the properties of these halo structures and their connection to the local circumgalactic and intergalactic medium (CGM and IGM, respectively) have been investigated in great detail by many different groups. So far it remains unclear, however, to what extent the results of these studies can be transferred to other galaxies in the local Universe. In this thesis, we study the absorption properties of Galactic HVCs and compare the HVC absorption characteristics with those of intervening QSO absorption-line systems at low redshift. The goal of this project is to improve our understanding of the spatial extent and physical conditions of gaseous galaxy halos in the local Universe. In the first part of the thesis we use HST /STIS ultraviolet spectra of more than 40 extragalactic background sources to statistically analyze the absorption properties of the HVCs in the Galactic halo. We determine fundamental absorption line parameters including covering fractions of different weakly/intermediately/highly ionized metals with a particular focus on SiII and MgII. Due to the similarity in the ionization properties of SiII and MgII, we are able to estimate the contribution of HVC-like halo structures to the cross section of intervening strong MgII absorbers at z = 0. Our study implies that only the most massive HVCs would be regarded as strong MgII absorbers, if the Milky Way halo would be seen as a QSO absorption line system from an exterior vantage point. Combining the observed absorption-cross section of Galactic HVCs with the well-known number density of intervening strong MgII absorbers at z = 0, we conclude that the contribution of infalling gas clouds (i.e., HVC analogs) in the halos of Milky Way-type galaxies to the cross section of strong MgII absorbers is 34\%. This result indicates that only about one third of the strong MgII absorption can be associated with HVC analogs around other galaxies, while the majority of the strong MgII systems possibly is related to galaxy outflows and winds. The second part of this thesis focuses on the properties of intervening metal absorbers at low redshift. The analysis of the frequency and physical conditions of intervening metal systems in QSO spectra and their relation to nearby galaxies offers new insights into the typical conditions of gaseous galaxy halos. One major aspect in our study was to regard intervening metal systems as possible HVC analogs. We perform a detailed analysis of absorption line properties and line statistics for 57 metal absorbers along 78 QSO sightlines using newly-obtained ultraviolet spectra obtained with HST /COS. We find clear evidence for bimodal distribution in the HI column density in the absorbers, a trend that we interpret as sign for two different classes of absorption systems (with HVC analogs at the high-column density end). With the help of the strong transitions of SiII λ1260, SiIII λ1206, and CIII λ977 we have set up Cloudy photoionization models to estimate the local ionization conditions, gas densities, and metallicities. We find that the intervening absorption systems studied by us have, on average, similar physical conditions as Galactic HVC absorbers, providing evidence that many of them represent HVC analogs in the vicinity of other galaxies. We therefore determine typical halo sizes for SiII, SiIII, and CIII for L = 0.01L∗ and L = 0.05L∗ galaxies. Based on the covering fractions of the different ions in the Galactic halo, we find that, for example, the typical halo size for SiIII is ∼ 160 kpc for L = 0.05L∗ galaxies. We test the plausibility of this result by searching for known galaxies close to the QSO sightlines and at similar redshifts as the absorbers. We find that more than 34\% of the measured SiIII absorbers have galaxies associated with them, with the majority of the absorbers indeed being at impact parameters ρ ≤160 kpc.}, language = {en} } @phdthesis{Schmidt2014, author = {Schmidt, Lukas}, title = {Aerosols and boundary layer structure over Arctic sea ice based on airborne lidar and dropsonde measurements}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-75076}, school = {Universit{\"a}t Potsdam}, pages = {vii, 98, xiii}, year = {2014}, abstract = {The atmosphere over the Arctic Ocean is strongly influenced by the distribution of sea ice and open water. Leads in the sea ice produce strong convective fluxes of sensible and latent heat and release aerosol particles into the atmosphere. They increase the occurrence of clouds and modify the structure and characteristics of the atmospheric boundary layer (ABL) and thereby influence the Arctic climate. In the course of this study aircraft measurements were performed over the western Arctic Ocean as part of the campaign PAMARCMIP 2012 of the Alfred Wegener Institute for Polar and Marine Research (AWI). Backscatter from aerosols and clouds within the lower troposphere and the ABL were measured with the nadir pointing Airborne Mobile Aerosol Lidar (AMALi) and dropsondes were launched to obtain profiles of meteorological variables. Furthermore, in situ measurements of aerosol properties, meteorological variables and turbulence were part of the campaign. The measurements covered a broad range of atmospheric and sea ice conditions. In this thesis, properties of the ABL over Arctic sea ice with a focus on the influence of open leads are studied based on the data from the PAMARCMIP campaign. The height of the ABL is determined by different methods that are applied to dropsonde and AMALi backscatter profiles. ABL heights are compared for different flights representing different conditions of the atmosphere and of sea ice and open water influence. The different criteria for ABL height that are applied show large variation in terms of agreement among each other, depending on the characteristics of the ABL and its history. It is shown that ABL height determination from lidar backscatter by methods commonly used under mid-latitude conditions is applicable to the Arctic ABL only under certain conditions. Aerosol or clouds within the ABL are needed as a tracer for ABL height detection from backscatter. Hence an aerosol source close to the surface is necessary, that is typically found under the present influence of open water and therefore convective conditions. However it is not always possible to distinguish residual layers from the actual ABL. Stable boundary layers are generally difficult to detect. To illustrate the complexity of the Arctic ABL and processes therein, four case studies are analyzed each of which represents a snapshot of the interplay between atmosphere and underlying sea ice or water surface. Influences of leads and open water on the aerosol and clouds within the ABL are identified and discussed. Leads are observed to cause the formation of fog and cloud layers within the ABL by humidity emission. Furthermore they decrease the stability and increase the height of the ABL and consequently facilitate entrainment of air and aerosol layers from the free troposphere.}, language = {en} } @article{PalyulinAlaNissilaMetzler2014, author = {Palyulin, Vladimir V. and Ala-Nissila, Tapio and Metzler, Ralf}, title = {Polymer translocation: the first two decades and the recent diversification}, series = {Soft matter}, volume = {45}, journal = {Soft matter}, number = {10}, editor = {Metzler, Ralf}, publisher = {the Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-76266}, pages = {9016 -- 9037}, year = {2014}, abstract = {Probably no other field of statistical physics at the borderline of soft matter and biological physics has caused such a flurry of papers as polymer translocation since the 1994 landmark paper by Bezrukov, Vodyanoy, and Parsegian and the study of Kasianowicz in 1996. Experiments, simulations, and theoretical approaches are still contributing novel insights to date, while no universal consensus on the statistical understanding of polymer translocation has been reached. We here collect the published results, in particular, the famous-infamous debate on the scaling exponents governing the translocation process. We put these results into perspective and discuss where the field is going. In particular, we argue that the phenomenon of polymer translocation is non-universal and highly sensitive to the exact specifications of the models and experiments used towards its analysis.}, language = {en} } @misc{PalyulinAlaNissilaMetzler2014, author = {Palyulin, Vladimir V. and Ala-Nissila, Tapio and Metzler, Ralf}, title = {Polymer translocation: the first two decades and the recent diversification}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-76287}, pages = {9016 -- 9037}, year = {2014}, abstract = {Probably no other field of statistical physics at the borderline of soft matter and biological physics has caused such a flurry of papers as polymer translocation since the 1994 landmark paper by Bezrukov, Vodyanoy, and Parsegian and the study of Kasianowicz in 1996. Experiments, simulations, and theoretical approaches are still contributing novel insights to date, while no universal consensus on the statistical understanding of polymer translocation has been reached. We here collect the published results, in particular, the famous-infamous debate on the scaling exponents governing the translocation process. We put these results into perspective and discuss where the field is going. In particular, we argue that the phenomenon of polymer translocation is non-universal and highly sensitive to the exact specifications of the models and experiments used towards its analysis.}, language = {en} } @article{JeonChechkinMetzler2014, author = {Jeon, Jae-Hyung and Chechkin, Aleksei V. and Metzler, Ralf}, title = {Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion}, series = {Physical chemistry, chemical physics : PCCP}, volume = {30}, journal = {Physical chemistry, chemical physics : PCCP}, number = {16}, publisher = {The Royal Society of Chemistry}, address = {Cambridge}, doi = {10.1039/C4CP02019G}, pages = {15811 -- 15817}, year = {2014}, abstract = {Anomalous diffusion is frequently described by scaled Brownian motion (SBM){,} a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is ?x2(t)? [similar{,} equals] 2K(t)t with K(t) [similar{,} equals] t[small alpha]-1 for 0 < [small alpha] < 2. SBM may provide a seemingly adequate description in the case of unbounded diffusion{,} for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely{,} we demonstrate that under confinement{,} the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments{,} in particular{,} under confinement inside cellular compartments or when optical tweezers tracking methods are used.}, language = {en} } @phdthesis{Brem2014, author = {Brem, Patrick}, title = {Compact objects in dense astrophysical environments}, school = {Universit{\"a}t Potsdam}, pages = {173}, year = {2014}, language = {en} } @phdthesis{Goswami2014, author = {Goswami, Bedartha}, title = {Uncertainties in climate data analysis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-78312}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {Scientific inquiry requires that we formulate not only what we know, but also what we do not know and by how much. In climate data analysis, this involves an accurate specification of measured quantities and a consequent analysis that consciously propagates the measurement errors at each step. The dissertation presents a thorough analytical method to quantify errors of measurement inherent in paleoclimate data. An additional focus are the uncertainties in assessing the coupling between different factors that influence the global mean temperature (GMT). Paleoclimate studies critically rely on `proxy variables' that record climatic signals in natural archives. However, such proxy records inherently involve uncertainties in determining the age of the signal. We present a generic Bayesian approach to analytically determine the proxy record along with its associated uncertainty, resulting in a time-ordered sequence of correlated probability distributions rather than a precise time series. We further develop a recurrence based method to detect dynamical events from the proxy probability distributions. The methods are validated with synthetic examples and demonstrated with real-world proxy records. The proxy estimation step reveals the interrelations between proxy variability and uncertainty. The recurrence analysis of the East Asian Summer Monsoon during the last 9000 years confirms the well-known `dry' events at 8200 and 4400 BP, plus an additional significantly dry event at 6900 BP. We also analyze the network of dependencies surrounding GMT. We find an intricate, directed network with multiple links between the different factors at multiple time delays. We further uncover a significant feedback from the GMT to the El Ni{\~n}o Southern Oscillation at quasi-biennial timescales. The analysis highlights the need of a more nuanced formulation of influences between different climatic factors, as well as the limitations in trying to estimate such dependencies.}, language = {en} } @phdthesis{Conrad2014, author = {Conrad, Claudia}, title = {Open cluster groups and complexes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-77605}, school = {Universit{\"a}t Potsdam}, pages = {xii, 172}, year = {2014}, abstract = {It is generally agreed upon that stars typically form in open clusters and stellar associations, but little is known about the structure of the open cluster system. Do open clusters and stellar associations form isolated or do they prefer to form in groups and complexes? Open cluster groups and complexes could verify star forming regions to be larger than expected, which would explain the chemical homogeneity over large areas in the Galactic disk. They would also define an additional level in the hierarchy of star formation and could be used as tracers for the scales of fragmentation in giant molecular clouds? Furthermore, open cluster groups and complexes could affect Galactic dynamics and should be considered in investigations and simulations on the dynamical processes, such as radial migration, disc heating, differential rotation, kinematic resonances, and spiral structure. In the past decade there were a few studies on open cluster pairs (de La Fuente Marcos \& de La Fuente Marcos 2009a,b,c) and on open cluster groups and complexes (Piskunov et al. 2006). The former only considered spatial proximity for the identification of the pairs, while the latter also required tangential velocities to be similar for the members. In this work I used the full set of 6D phase-space information to draw a more detailed picture on these structures. For this purpose I utilised the most homogeneous cluster catalogue available, namely the Catalogue of Open Cluster Data (COCD; Kharchenko et al. 2005a,b), which contains parameters for 650 open clusters and compact associations, as well as for their uniformly selected members. Additional radial velocity (RV) and metallicity ([M/H]) information on the members were obtained from the RAdial Velocity Experiment (RAVE; Steinmetz et al. 2006; Kordopatis et al. 2013) for 110 and 81 clusters, respectively. The RAVE sample was cleaned considering quality parameters and flags provided by RAVE (Matijevič et al. 2012; Kordopatis et al. 2013). To ensure that only real members were included for the mean values, also the cluster membership, as provided by Kharchenko et al. (2005a,b), was considered for the stars cross-matched in RAVE. 6D phase-space information could be derived for 432 out of the 650 COCD objects and I used an adaption of the Friends-of-Friends algorithm, as used in cosmology, to identify potential groupings. The vast majority of the 19 identified groupings were pairs, but I also found four groups of 4-5 members and one complex with 15 members. For the verification of the identified structures, I compared the results to a randomly selected subsample of the catalogue for the Milky Way global survey of Star Clusters (MWSC; Kharchenko et al. 2013), which became available recently, and was used as reference sample. Furthermore, I implemented Monte-Carlo simulations with randomised samples created from two distinguished input distributions for the spatial and velocity parameters. On the one hand, assuming a uniform distribution in the Galactic disc and, on the other hand, assuming the COCD data distributions to be representative for the whole open cluster population. The results suggested that the majority of identified pairs are rather by chance alignments, but the groups and the complex seemed to be genuine. A comparison of my results to the pairs, groups and complexes proposed in the literature yielded a partial overlap, which was most likely because of selection effects and different parameters considered. This is another verification for the existence of such structures. The characteristics of the found groupings favour that members of an open cluster grouping originate from a common giant molecular cloud and formed in a single, but possibly sequential, star formation event. Moreover, the fact that the young open cluster population showed smaller spatial separations between nearest neighbours than the old cluster population indicated that the lifetime of open cluster groupings is most likely comparable to that of the Galactic open cluster population itself. Still even among the old open clusters I could identify groupings, which suggested that the detected structure could be in some cases more long lived as one might think. In this thesis I could only present a pilot study on structures in the Galactic open cluster population, since the data sample used was highly incomplete. For further investigations a far more complete sample would be required. One step in this direction would be to use data from large current surveys, like SDSS, RAVE, Gaia-ESO and VVV, as well as including results from studies on individual clusters. Later the sample can be completed by data from upcoming missions, like Gaia and 4MOST. Future studies using this more complete open cluster sample will reveal the effect of open cluster groupings on star formation theory and their significance for the kinematics, dynamics and evolution of the Milky Way, and thereby of spiral galaxies.}, language = {en} } @phdthesis{Balzer2014, author = {Balzer, Arnim}, title = {Crab flare observations with H.E.S.S. phase II}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-72545}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {The H.E.S.S. array is a third generation Imaging Atmospheric Cherenkov Telescope (IACT) array. It is located in the Khomas Highland in Namibia, and measures very high energy (VHE) gamma-rays. In Phase I, the array started data taking in 2004 with its four identical 13 m telescopes. Since then, H.E.S.S. has emerged as the most successful IACT experiment to date. Among the almost 150 sources of VHE gamma-ray radiation found so far, even the oldest detection, the Crab Nebula, keeps surprising the scientific community with unexplained phenomena such as the recently discovered very energetic flares of high energy gamma-ray radiation. During its most recent flare, which was detected by the Fermi satellite in March 2013, the Crab Nebula was simultaneously observed with the H.E.S.S. array for six nights. The results of the observations will be discussed in detail during the course of this work. During the nights of the flare, the new 24 m × 32 m H.E.S.S. II telescope was still being commissioned, but participated in the data taking for one night. To be able to reconstruct and analyze the data of the H.E.S.S. Phase II array, the algorithms and software used by the H.E.S.S. Phase I array had to be adapted. The most prominent advanced shower reconstruction technique developed by de Naurois and Rolland, the template-based model analysis, compares real shower images taken by the Cherenkov telescope cameras with shower templates obtained using a semi-analytical model. To find the best fitting image, and, therefore, the relevant parameters that describe the air shower best, a pixel-wise log-likelihood fit is done. The adaptation of this advanced shower reconstruction technique to the heterogeneous H.E.S.S. Phase II array for stereo events (i.e. air showers seen by at least two telescopes of any kind), its performance using MonteCarlo simulations as well as its application to real data will be described.}, language = {en} } @phdthesis{Fischer2014, author = {Fischer, Jost Leonhardt}, title = {Nichtlineare Kopplungsmechanismen akustischer Oszillatoren am Beispiel der Synchronisation von Orgelpfeifen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71975}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {In dieser Arbeit werden nichtlineare Kopplungsmechanismen von akustischen Oszillatoren untersucht, die zu Synchronisation f{\"u}hren k{\"o}nnen. Aufbauend auf die Fragestellungen vorangegangener Arbeiten werden mit Hilfe theoretischer und experimenteller Studien sowie mit Hilfe numerischer Simulationen die Elemente der Tonentstehung in der Orgelpfeife und die Mechanismen der gegenseitigen Wechselwirkung von Orgelpfeifen identifiziert. Daraus wird erstmalig ein vollst{\"a}ndig auf den aeroakustischen und fluiddynamischen Grundprinzipien basierendes nichtlinear gekoppeltes Modell selbst-erregter Oszillatoren f{\"u}r die Beschreibung des Verhaltens zweier wechselwirkender Orgelpfeifen entwickelt. Die durchgef{\"u}hrten Modellrechnungen werden mit den experimentellen Befunden verglichen. Es zeigt sich, dass die Tonentstehung und die Kopplungsmechanismen von Orgelpfeifen durch das entwickelte Oszillatormodell in weiten Teilen richtig beschrieben werden. Insbesondere kann damit die Ursache f{\"u}r den nichtlinearen Zusammenhang von Kopplungsst{\"a}rke und Synchronisation des gekoppelten Zwei-Pfeifen Systems, welcher sich in einem nichtlinearen Verlauf der Arnoldzunge darstellt, gekl{\"a}rt werden. Mit den gewonnenen Erkenntnissen wird der Einfluss des Raumes auf die Tonentstehung bei Orgelpfeifen betrachtet. Daf{\"u}r werden numerische Simulationen der Wechselwirkung einer Orgelpfeife mit verschiedenen Raumgeometrien, wie z. B. ebene, konvexe, konkave, und gezahnte Geometrien, exemplarisch untersucht. Auch der Einfluss von Schwellk{\"a}sten auf die Tonentstehung und die Klangbildung der Orgelpfeife wird studiert. In weiteren, neuartigen Synchronisationsexperimenten mit identisch gestimmten Orgelpfeifen, sowie mit Mixturen wird die Synchronisation f{\"u}r verschiedene, horizontale und vertikale Pfeifenabst{\"a}nde in der Ebene der Schallabstrahlung, untersucht. Die dabei erstmalig beobachteten r{\"a}umlich isotropen Unstetigkeiten im Schwingungsverhalten der gekoppelten Pfeifensysteme, deuten auf abstandsabh{\"a}ngige Wechsel zwischen gegen- und gleichphasigen Sychronisationsregimen hin. Abschließend wird die M{\"o}glichkeit dokumentiert, das Ph{\"a}nomen der Synchronisation zweier Orgelpfeifen durch numerische Simulationen, also der Behandlung der kompressiblen Navier-Stokes Gleichungen mit entsprechenden Rand- und Anfangsbedingungen, realit{\"a}tsnah abzubilden. Auch dies stellt ein Novum dar.}, language = {de} } @phdthesis{Holler2014, author = {Holler, Markus}, title = {Photon reconstruction for the H.E.S.S. 28 m telescope and analysis of Crab Nebula and galactic centre observations}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-72099}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {In the presented thesis, the most advanced photon reconstruction technique of ground-based γ-ray astronomy is adapted to the H.E.S.S. 28 m telescope. The method is based on a semi-analytical model of electromagnetic particle showers in the atmosphere. The properties of cosmic γ-rays are reconstructed by comparing the camera image of the telescope with the Cherenkov emission that is expected from the shower model. To suppress the dominant background from charged cosmic rays, events are selected based on several criteria. The performance of the analysis is evaluated with simulated events. The method is then applied to two sources that are known to emit γ-rays. The first of these is the Crab Nebula, the standard candle of ground-based γ-ray astronomy. The results of this source confirm the expected performance of the reconstruction method, where the much lower energy threshold compared to H.E.S.S. I is of particular importance. A second analysis is performed on the region around the Galactic Centre. The analysis results emphasise the capabilities of the new telescope to measure γ-rays in an energy range that is interesting for both theoretical and experimental astrophysics. The presented analysis features the lowest energy threshold that has ever been reached in ground-based γ-ray astronomy, opening a new window to the precise measurement of the physical properties of time-variable sources at energies of several tens of GeV.}, language = {en} } @phdthesis{Trabant2014, author = {Trabant, Christoph}, title = {Ultrafast photoinduced phase transitions in complex materials probed by time-resolved resonant soft x-ray diffraction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71377}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {In processing and data storage mainly ferromagnetic (FM) materials are being used. Approaching physical limits, new concepts have to be found for faster, smaller switches, for higher data densities and more energy efficiency. Some of the discussed new concepts involve the material classes of correlated oxides and materials with antiferromagnetic coupling. Their applicability depends critically on their switching behavior, i.e., how fast and how energy efficient material properties can be manipulated. This thesis presents investigations of ultrafast non-equilibrium phase transitions on such new materials. In transition metal oxides (TMOs) the coupling of different degrees of freedom and resulting low energy excitation spectrum often result in spectacular changes of macroscopic properties (colossal magneto resistance, superconductivity, metal-to-insulator transitions) often accompanied by nanoscale order of spins, charges, orbital occupation and by lattice distortions, which make these material attractive. Magnetite served as a prototype for functional TMOs showing a metal-to-insulator-transition (MIT) at T = 123 K. By probing the charge and orbital order as well as the structure after an optical excitation we found that the electronic order and the structural distortion, characteristics of the insulating phase in thermal equilibrium, are destroyed within the experimental resolution of 300 fs. The MIT itself occurs on a 1.5 ps timescale. It shows that MITs in functional materials are several thousand times faster than switching processes in semiconductors. Recently ferrimagnetic and antiferromagnetic (AFM) materials have become interesting. It was shown in ferrimagnetic GdFeCo, that the transfer of angular momentum between two opposed FM subsystems with different time constants leads to a switching of the magnetization after laser pulse excitation. In addition it was theoretically predicted that demagnetization dynamics in AFM should occur faster than in FM materials as no net angular momentum has to be transferred out of the spin system. We investigated two different AFM materials in order to learn more about their ultrafast dynamics. In Ho, a metallic AFM below T ≈ 130 K, we found that the AFM Ho can not only be faster but also ten times more energy efficiently destroyed as order in FM comparable metals. In EuTe, an AFM semiconductor below T ≈ 10 K, we compared the loss of magnetization and laser-induced structural distortion in one and the same experiment. Our experiment shows that they are effectively disentangled. An exception is an ultrafast release of lattice dynamics, which we assign to the release of magnetostriction. The results presented here were obtained with time-resolved resonant soft x-ray diffraction at the Femtoslicing source of the Helmholtz-Zentrum Berlin and at the free-electron laser in Stanford (LCLS). In addition the development and setup of a new UHV-diffractometer for these experiments will be reported.}, language = {en} } @article{ZhaoDunlopQiuetal.2014, author = {Zhao, Qiang and Dunlop, John William Chapman and Qiu, Xunlin and Huang, Feihe and Zhang, Zibin and Heyda, Jan and Dzubiella, Joachim and Antonietti, Markus and Yuan, Jiayin}, title = {An instant multi-responsive porous polymer actuator driven by solvent molecule sorption}, series = {Nature Communications}, volume = {5}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms5293}, pages = {8}, year = {2014}, abstract = {Fast actuation speed, large-shape deformation and robust responsiveness are critical to synthetic soft actuators. A simultaneous optimization of all these aspects without trade-offs remains unresolved. Here we describe porous polymer actuators that bend in response to acetone vapour (24 kPa, 20 degrees C) at a speed of an order of magnitude faster than the state-of-the-art, coupled with a large-scale locomotion. They are meanwhile multi-responsive towards a variety of organic vapours in both the dry and wet states, thus distinctive from the traditional gel actuation systems that become inactive when dried. The actuator is easy-to-make and survives even after hydrothermal processing (200 degrees C, 24 h) and pressing-pressure (100 MPa) treatments. In addition, the beneficial responsiveness is transferable, being able to turn 'inert' objects into actuators through surface coating. This advanced actuator arises from the unique combination of porous morphology, gradient structure and the interaction between solvent molecules and actuator materials.}, language = {en} } @article{ZhangZhangYouetal.2014, author = {Zhang, Xiaoqing and Zhang, Xinwu and You, Qiong and Sessler, Gerhard M.}, title = {Low- cost, large- area, stretchable piezoelectric films based on irradiation- crosslinked poly ( propylene)}, series = {Macromolecular materials and engineering}, volume = {299}, journal = {Macromolecular materials and engineering}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1438-7492}, doi = {10.1002/mame.201300161}, pages = {290 -- 295}, year = {2014}, abstract = {Low cost, large area, lightweight, stretchable piezoelectric films, based on space-charge electret with a foam structure (i.e., ferroelectrets or piezoelectrets), have been fabricated by using commercially available irradiation cross-linked poly(propylene) (IXPP) foam sheets. Piezoelectric d(33) coefficients are as high as 100pCN(-1). The piezoelectric performance in such IXPP films is well preserved for repeated strains of less than 10\%. Piezoelectric d(33) coefficients are frequency independent in the range from 2 to 100Hz. Such new class materials may be applied in sensory skins, smart clothing, bio-inspired systems, microenergy harvesters, and so on.}, language = {en} } @phdthesis{Mallonn2014, author = {Mallonn, Matthias}, title = {Ground-based transmission spectroscopy of three inflated Hot Jupiter exoplanets}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-74403}, school = {Universit{\"a}t Potsdam}, pages = {ix, 115}, year = {2014}, abstract = {The characterization of exoplanets is a young and rapidly expanding field in astronomy. It includes a method called transmission spectroscopy that searches for planetary spectral fingerprints in the light received from the host star during the event of a transit. This techniques allows for conclusions on the atmospheric composition at the terminator region, the boundary between the day and night side of the planet. Observationally a big challenge, first attempts in the community have been successful in the detection of several absorption features in the optical wavelength range. These are for example a Rayleighscattering slope and absorption by sodium and potassium. However, other objects show a featureless spectrum indicative for a cloud or haze layer of condensates masking the probable atmospheric layers. In this work, we performed transmission spectroscopy by spectrophotometry of three Hot Jupiter exoplanets. When we began the work on this thesis, optical transmission spectra have been available for two exoplanets. Our main goal was to advance the current sample of probed objects to learn by comparative exoplanetology whether certain absorption features are common. We selected the targets HAT-P-12b, HAT-P-19b and HAT-P-32b, for which the detection of atmospheric signatures is feasible with current ground-based instrumentation. In addition, we monitored the host stars of all three objects photometrically to correct for influences of stellar activity if necessary. The obtained measurements of the three objects all favor featureless spectra. A variety of atmospheric compositions can explain the lack of a wavelength dependent absorption. But the broad trend of featureless spectra in planets of a wide range of temperatures, found in this work and in similar studies recently published in the literature, favors an explanation based on the presence of condensates even at very low concentrations in the atmospheres of these close-in gas giants. This result points towards the general conclusion that the capability of transmission spectroscopy to determine the atmospheric composition is limited, at least for measurements at low spectral resolution. In addition, we refined the transit parameters and ephemerides of HAT-P-12b and HATP- 19b. Our monitoring campaigns allowed for the detection of the stellar rotation period of HAT-P-19 and a refined age estimate. For HAT-P-12 and HAT-P-32, we derived upper limits on their potential variability. The calculated upper limits of systematic effects of starspots on the derived transmission spectra were found to be negligible for all three targets. Finally, we discussed the observational challenges in the characterization of exoplanet atmospheres, the importance of correlated noise in the measurements and formulated suggestions on how to improve on the robustness of results in future work.}, language = {en} } @article{KurfuerstFeldmeierKrticka2014, author = {Kurfuerst, P. and Feldmeier, Achim and Krticka, Jiri}, title = {Time-dependent modeling of extended thin decretion disks of critically rotating stars}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {569}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201424272}, pages = {7}, year = {2014}, abstract = {Context. During their evolution massive stars can reach the phase of critical rotation when a further increase in rotational speed is no longer possible. Direct centrifugal ejection from a critically or near-critically rotating surface forms a gaseous equatorial decretion disk. Anomalous viscosity provides the efficient mechanism for transporting the angular momentum outwards. The outer part of the disk can extend up to a very large distance from the parent star. Aims. We study the evolution of density, radial and azimuthal velocity, and angular momentum loss rate of equatorial decretion disks out to very distant regions. We investigate how the physical characteristics of the disk depend on the distribution of temperature and viscosity. Methods. We calculated stationary models using the Newton-Raphson method. For time-dependent hydrodynamic modeling we developed the numerical code based on an explicit finite difference scheme on an Eulerian grid including full Navier-Stokes shear viscosity. Results. The sonic point distance and the maximum angular momentum loss rate strongly depend on the temperature profile and are almost independent of viscosity. The rotational velocity at large radii rapidly drops accordingly to temperature and viscosity distribution. The total amount of disk mass and the disk angular momentum increase with decreasing temperature and viscosity. Conclusions. The time-dependent one-dimensional models basically confirm the results obtained in the stationary models as well as the assumptions of the analytical approximations. Including full Navier-Stokes viscosity we systematically avoid the rotational velocity sign change at large radii. The unphysical drop of the rotational velocity and angular momentum loss at large radii (present in some models) can be avoided in the models with decreasing temperature and viscosity.}, language = {en} } @unpublished{HenkelPieplow2014, author = {Henkel, Carsten and Pieplow, Gregor}, title = {Reply to Comment on 'Fully covariant radiation force on a polarizable particle'}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/11/118002}, pages = {8}, year = {2014}, abstract = {We argue that the theories of Volokitin and Persson (2014 New J. Phys. 16 118001), Dedkov and Kyasov (2008 J. Phys.: Condens. Matter 20 354006), and Pieplow and Henkel (2013 New J. Phys. 15 023027) agree on the electromagnetic force on a small, polarizable particle that is moving parallel to a planar, macroscopic body, as far as the contribution of evanescent waves is concerned. The apparent differences are discussed in detail and explained by choices of units and integral transformations. We point out in particular the role of the Lorentz contraction in the procedure used by Volokitin and Persson, where a macroscopic body is 'diluted' to obtain the force on a small particle. Differences that appear in the contribution of propagating photons are briefly mentioned.}, language = {en} } @article{HaakhHenkelSpagnoloetal.2014, author = {Haakh, Harald R. and Henkel, Carsten and Spagnolo, Salvatore and Rizzuto, Lucia and Passante, Roberto}, title = {Dynamical Casimir-Polder interaction between an atom and surface plasmons}, series = {Physical review : A, Atomic, molecular, and optical physics}, volume = {89}, journal = {Physical review : A, Atomic, molecular, and optical physics}, number = {2}, publisher = {American Physical Society}, address = {College Park}, issn = {1050-2947}, doi = {10.1103/PhysRevA.89.022509}, pages = {11}, year = {2014}, abstract = {We investigate the time-dependent Casimir-Polder potential of a polarizable two-level atom placed near a surface of arbitrary material, after a sudden change in the parameters of the system. Different initial conditions are taken into account. For an initially bare ground-state atom, the time-dependent Casimir-Polder energy reveals how the atom is "being dressed" by virtual, matter-assisted photons. We also study the transient behavior of the Casimir-Polder interaction between the atom and the surface starting from a partially dressed state, after an externally induced change in the atomic level structure or transition dipoles. The Heisenberg equations are solved through an iterative technique for both atomic and field operators in the medium-assisted electromagnetic field quantization scheme. We analyze, in particular, how the time evolution of the interaction energy depends on the optical properties of the surface, in particular on the dispersion relation of surface plasmon polaritons. The physical significance and the limits of validity of the obtained results are discussed in detail.}, language = {en} } @article{MkrtchianHenkel2014, author = {Mkrtchian, Vanik E. and Henkel, Carsten}, title = {On non-equilibrium photon distributions in the Casimir effect}, series = {Annalen der Physik}, volume = {526}, journal = {Annalen der Physik}, number = {1-2}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0003-3804}, doi = {10.1002/andp.201300135}, pages = {87 -- 101}, year = {2014}, abstract = {The electromagnetic field in a typical geometry of the Casimir effect is described in the Schwinger-Keldysh formalism. The main result is the photon distribution function (Keldysh Green function) in any stationary state of the field. A two-plate geometry with a sliding interface in local equilibrium is studied in detail, and full agreement with the results of Rytov fluctuation electrodynamics is found.}, language = {en} } @article{JoulainBenAbdallahChapuisetal.2014, author = {Joulain, Karl and Ben-Abdallah, Philippe and Chapuis, Pierre-Olivier and De Wilde, Y. and Babuty, A. and Henkel, Carsten}, title = {Strong tip-sample coupling in thermal radiation scanning tunneling microscopy}, series = {Journal of quantitative spectroscopy \& radiative transfer}, volume = {136}, journal = {Journal of quantitative spectroscopy \& radiative transfer}, publisher = {Elsevier}, address = {Oxford}, issn = {0022-4073}, doi = {10.1016/j.jqsrt.2013.12.006}, pages = {1 -- 15}, year = {2014}, language = {en} } @article{MiedemaBeyeKoenneckeetal.2014, author = {Miedema, P. S. and Beye, Martin and Koennecke, R. and Schiwietz, G. and F{\"o}hlisch, Alexander}, title = {The angular- and crystal-momentum transfer through electron-phonon coupling in silicon and silicon-carbide: similarities and differences}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/9/093056}, pages = {17}, year = {2014}, abstract = {Electron-phonon scattering has been studied for silicon carbide (6H-SiC) with resonant inelastic x-ray scattering at the silicon 2p edge. The observed electron-phonon scattering yields a crystal momentum transfer rate per average phonon in 6H-SiC of 1.8 fs(-1) while it is 0.2 fs(-1) in crystalline silicon. The angular momentum transfer rate per average phonon for 6H-SiC is 0.1 fs(-1), which is much higher than 0.0035 fs(-1) obtained for crystalline silicon in a previous study. The higher electron-phonon scattering rates in 6H-SiC are a result of the larger electron localization at the silicon atoms in 6H-SiC as compared to crystalline silicon. While delocalized valence electrons can screen effectively (part of) the electron-phonon interaction, this effect is suppressed for 6H-SiC in comparison to crystalline silicon. Smaller contributions to the difference in electron-phonon scattering rates between 6H-SiC and silicon arise from the lower atomic mass of carbon versus silicon and the difference in local symmetry.}, language = {en} } @article{GodecBauerMetzler2014, author = {Godec, Aljaz and Bauer, Maximilian and Metzler, Ralf}, title = {Collective dynamics effect transient subdiffusion of inert tracers in flexible gel networks}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/9/092002}, pages = {13}, year = {2014}, abstract = {Based on extensive Brownian dynamics simulations we study the thermal motion of a tracer bead in a cross-linked, flexible gel in the limit when the tracer particle size is comparable to or even larger than the equilibrium mesh size of the gel. The analysis of long individual trajectories of the tracer demonstrates the existence of pronounced transient anomalous diffusion. From the time averaged mean squared displacement and the time averaged van Hove correlation functions we elucidate the many-body origin of the non-Brownian tracer bead dynamics. Our results shed new light onto the ongoing debate over the physical origin of steric tracer interactions with structured environments.}, language = {en} } @article{Baushev2014, author = {Baushev, Anton N.}, title = {Relaxation of dark matter halos: how to match observational data?}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {569}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201322730}, pages = {8}, year = {2014}, abstract = {We show that moderate energy relaxation in the formation of dark matter halos invariably leads to profiles that match those observed in the central regions of galaxies. The density profile of the central region is universal and insensitive to either the seed perturbation shape or the details of the relaxation process. The profile has a central core; the multiplication of the central density by the core radius is almost independent of the halo mass, in accordance with observations. In the core area the density distribution behaves as an Einasto profile with low index (n similar to 0.5); it has an extensive region with rho proportional to r(-2) at larger distances. This is exactly the shape that observations suggest for the central region of galaxies. On the other hand, this shape does not fit the galaxy cluster profiles. A possible explanation of this fact is that the relaxation is violent in the case of galaxy clusters; however, it is not violent enough when galaxies or smaller dark matter structures are considered. We discuss the reasons for this.}, language = {en} } @article{KliemToeroekTitovetal.2014, author = {Kliem, Bernhard and Toeroek, Tibor and Titov, Viacheslav S. and Lionello, Roberto and Linker, Jon A. and Liu, Rui and Liu, Chang and Wang, Haimin}, title = {Slow rise and partial eruption of a double-decker filament. II. A double flux rope model}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {792}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/792/2/107}, pages = {10}, year = {2014}, abstract = {Force-free equilibria containing two vertically arranged magnetic flux ropes of like chirality and current direction are considered as a model for split filaments/prominences and filament-sigmoid systems. Such equilibria are constructed analytically through an extension of the methods developed in Titov \& Demoulin and numerically through an evolutionary sequence including shear flows, flux emergence, and flux cancellation in the photospheric boundary. It is demonstrated that the analytical equilibria are stable if an external toroidal (shear) field component exceeding a threshold value is included. If this component decreases sufficiently, then both flux ropes turn unstable for conditions typical of solar active regions, with the lower rope typically becoming unstable first. Either both flux ropes erupt upward, or only the upper rope erupts while the lower rope reconnects with the ambient flux low in the corona and is destroyed. However, for shear field strengths staying somewhat above the threshold value, the configuration also admits evolutions which lead to partial eruptions with only the upper flux rope becoming unstable and the lower one remaining in place. This can be triggered by a transfer of flux and current from the lower to the upper rope, as suggested by the observations of a split filament in Paper I. It can also result from tether-cutting reconnection with the ambient flux at the X-type structure between the flux ropes, which similarly influences their stability properties in opposite ways. This is demonstrated for the numerically constructed equilibrium.}, language = {en} } @article{GoychukKharchenko2014, author = {Goychuk, Igor and Kharchenko, Vasyl O.}, title = {Anomalous features of diffusion in corrugated potentials with spatial correlations: Faster than normal, and other surprises}, series = {Physical review letters}, volume = {113}, journal = {Physical review letters}, number = {10}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.113.100601}, pages = {5}, year = {2014}, abstract = {Normal diffusion in corrugated potentials with spatially uncorrelated Gaussian energy disorder famously explains the origin of non-Arrhenius exp[-sigma(2)/(k(B)T(2))] temperature dependence in disordered systems. Here we show that unbiased diffusion remains asymptotically normal also in the presence of spatial correlations decaying to zero. However, because of a temporal lack of self-averaging, transient subdiffusion emerges on the mesoscale, and it can readily reach macroscale even for moderately strong disorder fluctuations of sigma similar to 4 - 5k(B)T. Because of its nonergodic origin, such subdiffusion exhibits a large scatter in single-trajectory averages. However, at odds with intuition, it occurs essentially faster than one expects from the normal diffusion in the absence of correlations. We apply these results to diffusion of regulatory proteins on DNA molecules and predict that such diffusion should be anomalous, but much faster than earlier expected on a typical length of genes for a realistic energy disorder of several room k(B)T, or merely 0.05-0.075 eV.}, language = {en} } @misc{WinklerCherstvy2014, author = {Winkler, Roland G. and Cherstvy, Andrey G.}, title = {Strong and weak polyelectrolyte adsorption onto oppositely charged curved surfaces}, series = {Advances in polymer science}, volume = {255}, journal = {Advances in polymer science}, editor = {Muller, M.}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-642-40734-5; 978-3-642-40733-8}, issn = {0065-3195}, doi = {10.1007/12_2012_183}, pages = {1 -- 56}, year = {2014}, abstract = {Polyelectrolytes are macromolecules composed of charged monomers and exhibit unique properties due to the interplay of their flexibility and electrostatic interactions. In solution, they are attracted to oppositely charged surfaces and interfaces and exhibit a transition to an adsorbed state when certain conditions are met concerning the charge densities of the polymer and surface and the properties of the solution. In this review, we discuss two limiting cases for adsorption of flexible polyelectrolytes on curved surfaces: weak and strong adsorption. In the first case, adsorption is strongly influenced by the entropic degrees of freedom of a flexible polyelectrolyte. By contrast, in the strong adsorption limit, electrostatic interactions dominate, which leads to particular adsorption patterns, specifically on spherical surfaces. We discuss the corresponding theoretical approaches, applying a mean-field description for the polymer and the polymer-surface interaction. For weak adsorption, we discuss the critical adsorption behavior by exactly solvable models for planar and spherical geometries and a generic approximation scheme, which is additionally applied to cylindrical surfaces. For strong adsorption, we investigate various polyelectrolyte patterns on cylinders and spheres and evaluate their stability. The results are discussed in the light of experimental results, mostly of DNA adsorption experiments.}, language = {en} } @article{deCarvalhoMetzlerCherstvy2014, author = {de Carvalho, Sidney J. and Metzler, Ralf and Cherstvy, Andrey G.}, title = {Critical adsorption of polyelectrolytes onto charged Janus nanospheres}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {29}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp02207f}, pages = {15539 -- 15550}, year = {2014}, abstract = {Based on extensive Monte Carlo simulations and analytical considerations we study the electrostatically driven adsorption of flexible polyelectrolyte chains onto charged Janus nanospheres. These net-neutral colloids are composed of two equally but oppositely charged hemispheres. The critical binding conditions for polyelectrolyte chains are analysed as function of the radius of the Janus particle and its surface charge density, as well as the salt concentration in the ambient solution. Specifically for the adsorption of finite-length polyelectrolyte chains onto Janus nanoparticles, we demonstrate that the critical adsorption conditions drastically differ when the size of the Janus particle or the screening length of the electrolyte are varied. We compare the scaling laws obtained for the adsorption-desorption threshold to the known results for uniformly charged spherical particles, observing significant disparities. We also contrast the changes to the polyelectrolyte chain conformations close to the surface of the Janus nanoparticles as compared to those for simple spherical particles. Finally, we discuss experimentally relevant physicochemical systems for which our simulations results may become important. In particular, we observe similar trends with polyelectrolyte complexation with oppositely but heterogeneously charged proteins.}, language = {en} } @article{PalyulinChechkinMetzler2014, author = {Palyulin, Vladimir V. and Chechkin, Aleksei V. and Metzler, Ralf}, title = {Space-fractional Fokker-Planck equation and optimization of random search processes in the presence of an external bias}, series = {Journal of statistical mechanics: theory and experiment}, journal = {Journal of statistical mechanics: theory and experiment}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1742-5468}, doi = {10.1088/1742-5468/2014/11/P11031}, pages = {32}, year = {2014}, abstract = {Based on the space-fractional Fokker-Planck equation with a delta-sink term, we study the efficiency of random search processes based on Levy flights with power-law distributed jump lengths in the presence of an external drift, for instance, an underwater current, an airflow, or simply the preference of the searcher based on prior experience. While Levy flights turn out to be efficient search processes when the target is upstream relative to the starting point, in the downstream scenario, regular Brownian motion turns out to be advantageous. This is caused by the occurrence of leapovers of Levy flights, due to which Levy flights typically overshoot a point or small interval. Studying the solution of the fractional Fokker-Planck equation, we establish criteria when the combination of the external stream and the initial distance between the starting point and the target favours Levy flights over the regular Brownian search. Contrary to the common belief that Levy flights with a Levy index alpha = 1 (i.e. Cauchy flights) are optimal for sparse targets, we find that the optimal value for alpha may range in the entire interval (1, 2) and explicitly include Brownian motion as the most efficient search strategy overall.}, language = {en} } @article{HeuerRaabeMenzel2014, author = {Heuer, Axel and Raabe, S. and Menzel, Ralf}, title = {Phase memory across two single-photon interferometers including wavelength conversion}, series = {Physical review : A, Atomic, molecular, and optical physics}, volume = {90}, journal = {Physical review : A, Atomic, molecular, and optical physics}, number = {4}, publisher = {American Physical Society}, address = {College Park}, issn = {1050-2947}, doi = {10.1103/PhysRevA.90.045803}, pages = {4}, year = {2014}, abstract = {Spontaneous parametric down-conversion (SPDC) in a nonlinear crystal generates two single photons (signal and idler) with random phases. Thus, no first-order interference between them occurs. However, coherence can be induced in a cascaded setup of two crystals if, e.g., the idler modes of both crystals are aligned to be indistinguishable. Due to the effect of phase memory it is found that the first-order interference of the signal beams can be controlled by the phase delay between the pump beams. Even for pump photon delays much larger than the coherence length of the SPDC photons, the visibility is above 90\%. The high visibilities reported here prove an almost perfect phase memory effect across the two interferometers for the pump and the signal photon modes.}, language = {en} } @article{GerhardtEckeWalzetal.2014, author = {Gerhardt, Matthias and Ecke, Mary and Walz, Michael and Stengl, Andreas and Beta, Carsten and Gerisch, G{\"u}nther}, title = {Actin and PIP3 waves in giant cells reveal the inherent length scale of an excited state}, series = {Journal of cell science}, volume = {127}, journal = {Journal of cell science}, number = {20}, publisher = {Company of Biologists Limited}, address = {Cambridge}, issn = {0021-9533}, doi = {10.1242/jcs.156000}, pages = {4507 -- 4517}, year = {2014}, abstract = {The membrane and actin cortex of a motile cell can autonomously differentiate into two states, one typical of the front, the other of the tail. On the substrate-attached surface of Dictyostelium discoideum cells, dynamic patterns of front-like and tail-like states are generated that are well suited to monitor transitions between these states. To image large-scale pattern dynamics independently of boundary effects, we produced giant cells by electric-pulse-induced cell fusion. In these cells, actin waves are coupled to the front and back of phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-rich bands that have a finite width. These composite waves propagate across the plasma membrane of the giant cells with undiminished velocity. After any disturbance, the bands of PIP3 return to their intrinsic width. Upon collision, the waves locally annihilate each other and change direction; at the cell border they are either extinguished or reflected. Accordingly, expanding areas of progressing PIP3 synthesis become unstable beyond a critical radius, their center switching from a front-like to a tail-like state. Our data suggest that PIP3 patterns in normal-sized cells are segments of the self-organizing patterns that evolve in giant cells.}, language = {en} } @article{Goychuk2014, author = {Goychuk, Igor}, title = {Life and death of stationary linear response in anomalous continuous time random walk dynamics}, series = {Communications in theoretical physics : a series journal of the Chinese Physical Society (A)}, volume = {62}, journal = {Communications in theoretical physics : a series journal of the Chinese Physical Society (A)}, number = {4}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0253-6102}, pages = {497 -- 504}, year = {2014}, abstract = {Linear theory of stationary response in systems at thermal equilibrium requires to find equilibrium correlation function of unperturbed responding system. Studies of the response of the systems exhibiting anomalously slow dynamics are often based on the continuous time random walk description (CTRW) with divergent mean waiting times. The bulk of the literature on anomalous response contains linear response functions like one by Cole-Cole calculated from such a CTRW theory and applied to systems at thermal equilibrium. Here we show within a fairly simple and general model that for the systems with divergent mean waiting times the stationary response at thermal equilibrium is absent, in accordance with some recent studies. The absence of such stationary response (or dying to zero non-stationary response in aging experiments) would confirm CTRW with divergent mean waiting times as underlying physical relaxation mechanism, but reject it otherwise. We show that the absence of stationary response is closely related to the breaking of ergodicity of the corresponding dynamical variable. As an important new result, we derive a generalized Cole-Cole response within ergodic CTRW dynamics with finite waiting time. Moreover, we provide a physically reasonable explanation of the origin and wide presence of 1/f noise in condensed matter for ergodic dynamics close to normal, rather than strongly deviating.}, language = {en} } @article{MeibohmSchreckWernet2014, author = {Meibohm, Jan and Schreck, Simon and Wernet, Philippe}, title = {Temperature dependent soft x-ray absorption spectroscopy of liquids}, series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, volume = {85}, journal = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, number = {10}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0034-6748}, doi = {10.1063/1.4896977}, pages = {7}, year = {2014}, abstract = {A novel sample holder is introduced which allows for temperature dependent soft x-ray absorption spectroscopy of liquids in transmission mode. The setup is based on sample cells with x-ray transmissive silicon nitride windows. A cooling circuit allows for temperature regulation of the sample liquid between -10 degrees C and +50 degrees C. The setup enables to record soft x-ray absorption spectra of liquids in transmission mode with a temperature resolution of 0.5K and better. Reliability and reproducibility of the spectra are demonstrated by investigating the characteristic temperature-induced changes in the oxygen K-edge x-ray absorption spectrum of liquid water. These are compared to the corresponding changes in the oxygen K-edge spectra from x-ray Raman scattering. (C) 2014 AIP Publishing LLC.}, language = {en} } @article{MicciullaDodooChevignyetal.2014, author = {Micciulla, Samantha and Dodoo, Samuel and Chevigny, Chloe and Laschewsky, Andr{\´e} and von Klitzing, Regine}, title = {Short versus long chain polyelectrolyte multilayers: a direct comparison of self-assembly and structural properties}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {40}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp03439b}, pages = {21988 -- 21998}, year = {2014}, abstract = {Successful layer-by-layer (LbL) growth of short chain (similar to 30 repeat units per chain) poly(sodium styrene sulfonate) (PSS)-poly(diallyl dimethylammonium chloride) (PDADMAC) multilayers is presented for the first time and compared with the growth of equivalent long chain polyelectrolyte multilayers (PEMs). A detailed study performed by quartz crystal microbalance with dissipation (QCM-D) is carried out and three main processes are identified: (i) initial mass uptake, (ii) adsorption desorption during layer equilibration and (iii) desorption during rinsing. In contrast to the high stability and strong layer increment of high molecular weight (HMW) PEMs, layer degradation characterizes low molecular weight (LMW) multilayers. In particular, two different instability phenomena are observed: a constant decrease of sensed mass during equilibration after PDADMAC adsorption, and a strong mass toss by salt-free rinsing after PSS adsorption. Yet, an increase of salt concentration leads to much stronger layer growth. First, when the rinsing medium is changed from pure water to 0.1 M NaCl, the mass loss during rinsing is reduced, irrespective of molecular weight. Second, an increase in salt concentration in the LMW PE solutions causes a larger increment during the initial adsorption step, with no effect on the rinsing. Finally, the mechanical properties of the two systems are extracted from the measured frequency and dissipation shifts, as they offer a deeper insight into the multilayer structures depending on chain length and outermost layer. The paper enriches the field of PE assembly by presenting the use of very short PE chains to form multilayers and elucidates the role of preparation conditions to overcome the limitation of layer stability.}, language = {en} } @article{ChuBrennerChenetal.2014, author = {Chu, X. -L. and Brenner, Thomas J. K. and Chen, X. -W. and Ghosh, Y. and Hollingsworth, J. A. and Sandoghdar, Vahid and Goetzinger, S.}, title = {Experimental realization of an optical antenna designed for collecting 99\% of photons from a quantum emitter}, series = {Optica}, volume = {1}, journal = {Optica}, number = {4}, publisher = {Optical Society of America}, address = {Washington}, issn = {2334-2536}, doi = {10.1364/OPTICA.1.000203}, pages = {203 -- 208}, year = {2014}, abstract = {A light source that emits single photons at well-defined times and into a well-defined mode would be a decisive asset for quantum information processing, quantum metrology, and sub-shot-noise detection of absorption. One of the central challenges in the realization of such a deterministic device based on a single quantum emitter concerns the collection of the photons, which are radiated into a 4 pi solid angle. Here, we present the fabrication and characterization of an optical antenna designed to convert the dipolar radiation of an arbitrarily oriented quantum emitter to a directional beam with more than 99\% efficiency. Our approach is extremely versatile and can be used for more efficient detection of nanoscopic emitters ranging from semiconductor quantum dots to dye molecules, color centers, or rare-earth ions in various environments. Having addressed the issue of collection efficiency, we also discuss the photophysical limitations of the existing quantum emitters for the realization of a deterministic single-photon source. (C) 2014 Optical Society of America}, language = {en} } @article{NezhadhaghighiChechkinMetzler2014, author = {Nezhadhaghighi, M. Ghasemi and Chechkin, Aleksei V. and Metzler, Ralf}, title = {Numerical approach to unbiased and driven generalized elastic model}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {140}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {2}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4858425}, pages = {9}, year = {2014}, abstract = {From scaling arguments and numerical simulations, we investigate the properties of the generalized elastic model (GEM) that is used to describe various physical systems such as polymers, membranes, single-file systems, or rough interfaces. We compare analytical and numerical results for the subdiffusion exponent beta characterizing the growth of the mean squared displacement <(delta h)(2)> of the field h described by the GEM dynamic equation. We study the scaling properties of the qth order moments with time, finding that the interface fluctuations show no intermittent behavior. We also investigate the ergodic properties of the process h in terms of the ergodicity breaking parameter and the distribution of the time averaged mean squared displacement. Finally, we study numerically the driven GEM with a constant, localized perturbation and extract the characteristics of the average drift for a tagged probe.}, language = {en} } @article{EmelianovaKuznetsovTurukina2014, author = {Emelianova, Yulia P. and Kuznetsov, A. P. and Turukina, Ludmila V.}, title = {Quasi-periodic bifurcations and "amplitude death" in low-dimensional ensemble of van der Pol oscillators}, series = {Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics}, volume = {378}, journal = {Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics}, number = {3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0375-9601}, doi = {10.1016/j.physleta.2013.10.049}, pages = {153 -- 157}, year = {2014}, abstract = {The dynamics of the four dissipatively coupled van der Pol oscillators is considered. Lyapunov chart is presented in the parameter plane. Its arrangement is discussed. We discuss the bifurcations of tori in the system at large frequency detuning of the oscillators. Here are quasi-periodic saddle-node, Hopf and Neimark-Sacker bifurcations. The effect of increase of the threshold for the "amplitude death" regime and the possibilities of complete and partial broadband synchronization are revealed.}, language = {en} } @article{Stephan2014, author = {Stephan, Christoph A.}, title = {A dark sector extension of the almost-commutative standard model}, series = {International journal of modern physics : A, Particles and fields, gravitation, cosmology, nuclear physics}, volume = {29}, journal = {International journal of modern physics : A, Particles and fields, gravitation, cosmology, nuclear physics}, number = {1}, publisher = {World Scientific}, address = {Singapore}, issn = {0217-751X}, doi = {10.1142/S0217751X14500055}, pages = {30}, year = {2014}, abstract = {We consider an extension of the Standard Model within the framework of Noncommutative Geometry. The model is based on an older model [C. A. Stephan, Phys. Rev. D 79, 065013 (2009)] which extends the Standard Model by new fermions, a new U(1)-gauge group and, crucially, a new scalar field which couples to the Higgs field. This new scalar field allows to lower the mass of the Higgs mass from similar to 170 GeV, as predicted by the Spectral Action for the Standard Model, to a value of 120-130 GeV. The shortcoming of the previous model lay in its inability to meet all the constraints on the gauge couplings implied by the Spectral Action. These shortcomings are cured in the present model which also features a "dark sector" containing fermions and scalar particles.}, language = {en} } @misc{PalyulinAlaNissilaMetzler2014, author = {Palyulin, Vladimir V. and Ala-Nissila, Tapio and Metzler, Ralf}, title = {Polymer translocation: the first two decades and the recent diversification}, series = {Soft matter}, volume = {10}, journal = {Soft matter}, number = {45}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c4sm01819b}, pages = {9016 -- 9037}, year = {2014}, abstract = {Probably no other field of statistical physics at the borderline of soft matter and biological physics has caused such a flurry of papers as polymer translocation since the 1994 landmark paper by Bezrukov, Vodyanoy, and Parsegian and the study of Kasianowicz in 1996. Experiments, simulations, and theoretical approaches are still contributing novel insights to date, while no universal consensus on the statistical understanding of polymer translocation has been reached. We here collect the published results, in particular, the famous-infamous debate on the scaling exponents governing the translocation process. We put these results into perspective and discuss where the field is going. In particular, we argue that the phenomenon of polymer translocation is non-universal and highly sensitive to the exact specifications of the models and experiments used towards its analysis.}, language = {en} } @article{PalyulinMetzler2014, author = {Palyulin, Vladimir V. and Metzler, Ralf}, title = {Speeding up the first-passage for subdiffusion by introducing a finite potential barrier}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {47}, journal = {Journal of physics : A, Mathematical and theoretical}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8113/47/3/032002}, pages = {13}, year = {2014}, abstract = {We show that for a subdiffusive continuous time random walk with scale-free waiting time distribution the first-passage dynamics on a finite interval can be optimized by introduction of a piecewise linear potential barrier. Analytical results for the survival probability and first-passage density based on the fractional Fokker-Planck equation are shown to agree well with Monte Carlo simulations results. As an application we discuss an improved design for efficient translocation of gradient copolymers compared to homopolymer translocation in a quasi-equilibrium approximation.}, language = {en} } @article{AliuArchambaultAuneetal.2014, author = {Aliu, E. and Archambault, S. and Aune, T. and Benbow, W. and Berger, K. and Bird, R. and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, W. and Dumm, J. and Errando, M. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krennrich, F. and Kumar, S. and Lang, M. J. and Lyutikov, M. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Mukherjee, R. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, M. and Popkow, A. and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Sheidaei, F. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zajczyk, A. and Zitzer, B.}, title = {A search for enhanced very high energy GAMMA-RAY emission from the 2013 march crab nebula flare}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters}, volume = {781}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {2041-8205}, doi = {10.1088/2041-8205/781/1/L11}, pages = {7}, year = {2014}, abstract = {In 2013 March, a flaring episode from the Crab Nebula lasting similar to 2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux change seen in the Fermi-LAT band >100 MeV during the period of simultaneous observations, the linear correlation factor can be constrained to be at most 8.6 x 10(-3) with 95\% confidence.}, language = {en} } @article{SpahnVieiraNetoGuimaraesetal.2014, author = {Spahn, Frank and Vieira Neto, E. and Guimaraes, A. H. F. and Gorban, A. N. and Brilliantov, Nikolai V.}, title = {A statistical model of aggregate fragmentation}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/1/013031}, pages = {11}, year = {2014}, abstract = {A statistical model of fragmentation of aggregates is proposed, based on the stochastic propagation of cracks through the body. The propagation rules are formulated on a lattice and mimic two important features of the process-a crack moves against the stress gradient while dissipating energy during its growth. We perform numerical simulations of the model for two-dimensional lattice and reveal that the mass distribution for small-and intermediate-size fragments obeys a power law, F(m) proportional to m(-3/2), in agreement with experimental observations. We develop an analytical theory which explains the detected power law and demonstrate that the overall fragment mass distribution in our model agrees qualitatively with that one observed in experiments.}, language = {en} } @article{GerhardtWalzBeta2014, author = {Gerhardt, Matthias and Walz, Michael and Beta, Carsten}, title = {Signaling in chemotactic amoebae remains spatially confined to stimulated membrane regions}, series = {Journal of cell science}, volume = {127}, journal = {Journal of cell science}, number = {23}, publisher = {Company of Biologists Limited}, address = {Cambridge}, issn = {0021-9533}, doi = {10.1242/jcs.161133}, pages = {5115 -- 5125}, year = {2014}, abstract = {Recent work has demonstrated that the receptor-mediated signaling system in chemotactic amoeboid cells shows typical properties of an excitable system. Here, we delivered spatially confined stimuli of the chemoattractant cAMP to the membrane of differentiated Dictyostelium discoideum cells to investigate whether localized receptor stimuli can induce the spreading of excitable waves in the G-protein-dependent signal transduction system. By imaging the spatiotemporal dynamics of fluorescent markers for phosphatidylinositol (3,4,5)-trisphosphate (PIP3), PTEN and filamentous actin, we observed that the activity of the signaling pathway remained spatially confined to the stimulated membrane region. Neighboring parts of the membrane were not excited and no receptor-initiated spatial spreading of excitation waves was observed. To generate localized cAMP stimuli, either particles that carried covalently bound cAMP molecules on their surface were brought into contact with the cell or a patch of the cell membrane was aspirated into a glass micropipette to shield this patch against freely diffusing cAMP molecules in the surrounding medium. Additionally, the binding site of the cAMP receptor was probed with different surface-immobilized cAMP molecules, confirming results from earlier ligand-binding studies.}, language = {en} } @article{SandersLomholtLizanaetal.2014, author = {Sanders, Lloyd P. and Lomholt, Michael A. and Lizana, Ludvig and Fogelmark, Karl and Metzler, Ralf and Ambjoernsson, Tobias}, title = {Severe slowing-down and universality of the dynamics in disordered interacting many-body systems: ageing and ultraslow diffusion}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/11/113050}, pages = {14}, year = {2014}, abstract = {Low-dimensional, many-body systems are often characterized by ultraslow dynamics. We study a labelled particle in a generic system of identical particles with hard-core interactions in a strongly disordered environment. The disorder is manifested through intermittent motion with scale-free sticking times at the single particle level. While for a non-interacting particle we find anomalous diffusion of the power-law form < x(2)(t)> similar or equal to t(alpha) of the mean squared displacement with 0 < alpha < 1, we demonstrate here that the combination of the disordered environment with the many-body interactions leads to an ultraslow, logarithmic dynamics < x(2)(t)> similar or equal to log(1/2)t with a universal 1/2 exponent. Even when a characteristic sticking time exists but the fluctuations of sticking times diverge we observe the mean squared displacement < x(2)(t)> similar or equal to t(gamma) with 0 < gamma < 1/2, that is slower than the famed Harris law < x(2)(t)> similar or equal to t(1/2) without disorder. We rationalize the results in terms of a subordination to a counting process, in which each transition is dominated by the forward waiting time of an ageing continuous time process.}, language = {en} } @article{EvansMurphyWhitmoreetal.2014, author = {Evans, T. M. and Murphy, M. T. and Whitmore, J. B. and Misawa, T. and Centurion, Martin and Lopez, S. and Martins, C. J. A. P. and Molaro, P. and Petitjean, P. and Rahmani, H. and Srianand, R. and Wendt, Martin}, title = {The UVES Large Program for testing fundamental physics - III. Constraints on the fine-structure constant from three telescopes}, series = {Monthly notices of the Royal Astronomical Society}, volume = {445}, journal = {Monthly notices of the Royal Astronomical Society}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stu1754}, pages = {128 -- 150}, year = {2014}, language = {en} } @article{ZamponiPenfoldNachtegaaletal.2014, author = {Zamponi, Flavio and Penfold, Thomas J. and Nachtegaal, Maarten and Luebcke, Andrea and Rittmann, Jochen and Milne, Chris J. and Chergui, Majed and van Bokhoven, Jeroen A.}, title = {Probing the dynamics of plasmon-excited hexanethiol-capped gold nanoparticles by picosecond X-ray absorption spectroscopy}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {42}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp03301a}, pages = {23157 -- 23163}, year = {2014}, abstract = {Picosecond X-ray absorption spectroscopy (XAS) is used to investigate the electronic and structural dynamics initiated by plasmon excitation of 1.8 nm diameter Au nanoparticles (NPs) functionalised with 1-hexanethiol. We show that 100 ps after photoexcitation the transient XAS spectrum is consistent with an 8\% expansion of the Au-Au bond length and a large increase in disorder associated with melting of the NPs. Recovery of the ground state occurs with a time constant of similar to 1.8 ns, arising from thermalisation with the environment. Simulations reveal that the transient spectrum exhibits no signature of charge separation at 100 ps and allows us to estimate an upper limit for the quantum yield (QY) of this process to be <0.1.}, language = {en} } @article{MetzlerSandersLomholtetal.2014, author = {Metzler, Ralf and Sanders, L. and Lomholt, M. A. and Lizana, L. and Fogelmark, K. and Ambjoernsson, Tobias}, title = {Ageing single file motion}, series = {The European physical journal}, volume = {223}, journal = {The European physical journal}, number = {14}, publisher = {Springer}, address = {Heidelberg}, issn = {1951-6355}, doi = {10.1140/epjst/e2014-02333-5}, pages = {3287 -- 3293}, year = {2014}, language = {en} } @article{LouisPuschmannKliemetal.2014, author = {Louis, Rohan E. and Puschmann, Klaus G. and Kliem, Bernhard and Balthasar, Horst and Denker, Carsten}, title = {Sunspot splitting triggering an eruptive flare}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {562}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201321106}, pages = {15}, year = {2014}, abstract = {Aims. We investigate how the splitting of the leading sunspot and associated flux emergence and cancellation in active region NOAA 11515 caused an eruptive M5.6 flare on 2012 July 2. Methods. Continuum intensity, line-of-sight magnetogram, and dopplergram data of the Helioseismic and Magnetic Imager were employed to analyse the photospheric evolution. Filtergrams in H alpha and He I 10830 angstrom of the Chromospheric Telescope at the Observatorio del Teide, Tenerife, track the evolution of the flare. The corresponding coronal conditions were derived from 171 angstrom and 304 angstrom images of the Atmospheric Imaging Assembly. Local correlation tracking was utilized to determine shear flows. Results. Emerging flux formed a neutral line ahead of the leading sunspot and new satellite spots. The sunspot splitting caused a long-lasting flow towards this neutral line, where a filament formed. Further flux emergence, partly of mixed polarity, as well as episodes of flux cancellation occurred repeatedly at the neutral line. Following a nearby C-class precursor flare with signs of interaction with the filament, the filament erupted nearly simultaneously with the onset of the M5.6 flare and evolved into a coronal mass ejection. The sunspot stretched without forming a light bridge, splitting unusually fast (within about a day, complete approximate to 6 h after the eruption) in two nearly equal parts. The front part separated strongly from the active region to approach the neighbouring active region where all its coronal magnetic connections were rooted. It also rotated rapidly (by 4.9 degrees h(-1)) and caused significant shear flows at its edge. Conclusions. The eruption resulted from a complex sequence of processes in the (sub-)photosphere and corona. The persistent flows towards the neutral line likely caused the formation of a flux rope that held the filament. These flows, their associated flux cancellation, the emerging flux, and the precursor flare all contributed to the destabilization of the flux rope. We interpret the sunspot splitting as the separation of two flux bundles differently rooted in the convection zone and only temporarily joined in the spot. This explains the rotation as the continued rise of the separating flux, and it implies that at least this part of the sunspot was still connected to its roots deep in the convection zone.}, language = {en} } @article{AliuArchambaultArlenetal.2014, author = {Aliu, E. and Archambault, S. and Arlen, T. and Aune, T. and Behera, B. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, W. and Duke, C. and Dumm, J. and Errando, M. and Falcone, A. and Federici, S. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Lang, M. J. and Madhavan, A. S. and Maier, G. and Majumdar, P. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, M. and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Varlotta, A. and Vassiliev, V. V. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zajczyk, A. and Zitzer, B.}, title = {A three-year multi-wavelenght study of the very-high-energy gamma-ray Blazar 1ES 0229+200}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {782}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/782/1/13}, pages = {12}, year = {2014}, language = {en} } @article{ToeroekLeakeTitovetal.2014, author = {Toeroek, T. and Leake, J. E. and Titov, Viacheslav S. and Archontis, V. and Mikic, Z. and Linton, M. G. and Dalmasse, K. and Aulanier, Guillaume and Kliem, Bernhard}, title = {Distribution of electric currents in solar active regions}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters}, volume = {782}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {2041-8205}, doi = {10.1088/2041-8205/782/1/L10}, pages = {6}, year = {2014}, language = {en} } @article{AcciariArlenAuneetal.2014, author = {Acciari, V. A. and Arlen, T. and Aune, T. and Benbow, W. and Bird, R. and Bouvier, A. and Bradbury, S. M. and Buckley, J. H. and Bugaev, V. and de la Calle Perez, I. and Carter-Lewis, D. A. and Cesarini, A. and Ciupik, L. and Collins-Hughes, E. and Connolly, M. P. and Cui, W. and Duke, C. and Dumm, J. and Falcone, A. and Federici, Simone and Fegan, D. J. and Fegan, S. J. and Finley, J. P. and Finnegan, G. and Fortson, L. and Gaidos, J. and Galante, N. and Gall, D. and Gibbs, K. and Gillanders, G. H. and Griffin, S. and Grube, J. and Gyuk, G. and Hanna, D. and Horan, D. and Humensky, T. B. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Lang, M. J. and McEnery, J. E. and Madhavan, A. S. and Moriarty, P. and Nelson, T. and Ong, R. A. and Orr, M. and Otte, A. N. and Perkins, J. S. and Petry, D. and Pichel, A. and Pohl, M. and Quinn, J. and Ragan, K. and Reynolds, T. and Roache, E. and Rovero, A. and Schroedter, M. and Sembroski, G. H. and Smith, A. and Telezhinsky, Igor O. and Theiling, M. and Toner, J. and Tyler, J. and Varlotta, A. and Vivier, M. and Wakely, S. P. and Ward, J. E. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Williams, D. A. and Wissel, S.}, title = {Observation of Markarian 421 in TeV gamma rays over a 14-year time span}, series = {Astroparticle physics}, volume = {54}, journal = {Astroparticle physics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-6505}, doi = {10.1016/j.astropartphys.2013.10.004}, pages = {1 -- 10}, year = {2014}, abstract = {The variability of the blazar Markarian 421 in TeV gamma rays over a 14-year time period has been explored with the Whipple 10 m telescope. It is shown that the dynamic range of its flux variations is large and similar to that in X-rays. A correlation between the X-ray and TeV energy bands is observed during some bright flares and when the complete data sets are binned on long timescales. The main database consists of 878.4 h of observation with the Whipple telescope, spread over 783 nights. The peak energy response of the telescope was 400 GeV with 20\% uncertainty. This is the largest database of any TeV-emitting active galactic nucleus (AGN) and hence was used to explore the variability profile of Markarian 421. The tithe-averaged flux from Markarian 421 over this period was 0.446 +/- 0.008 Crab flux units. The flux exceeded 10 Crab flux units on three separate occasions. For the 2000-2001 season the average flux reached 1.86 Crab units, while in the 1996-1997 season the average flux was only 0.23 Crab units.}, language = {en} } @article{BalzerFuesslingGajdusetal.2014, author = {Balzer, Arnim and Fuessling, M. and Gajdus, M. and Goering, D. and Lopatin, A. and de Naurois, M. and Schlenker, S. and Schwanke, U. and Stegmann, Christian}, title = {The HESS central data acquisition system}, series = {Astroparticle physics}, volume = {54}, journal = {Astroparticle physics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-6505}, doi = {10.1016/j.astropartphys.2013.11.007}, pages = {67 -- 80}, year = {2014}, language = {en} } @unpublished{Buerger2014, author = {B{\"u}rger, Gerd}, title = {Comment on "Bias correction, quantile mapping, and downscaling: revisiting the inflation issue"}, series = {Journal of climate}, volume = {27}, journal = {Journal of climate}, number = {4}, publisher = {American Meteorological Soc.}, address = {Boston}, issn = {0894-8755}, doi = {10.1175/JCLI-D-13-00184.1}, pages = {1819 -- 1820}, year = {2014}, abstract = {In a recent paper, Maraun describes the adverse effects of quantile mapping on downscaling. He argues that when large-scale GCM variables are rescaled directly to small-scale fields or even station data, genuine small-scale covariability is lost and replaced by uniform variability inherited from the larger scales. This leads to a misrepresentation mainly of areal means and long-term trends. This comment acknowledges the former point, although the argument is relatively old, but disagrees with the latter, showing that grid-size long-term trends can be different from local trends. Finally, because it is partly incorrectly addressed, some clarification is added regarding the inflation issue, stressing that neither randomization nor inflation is free of unverified assumptions.}, language = {en} } @article{ZinkWernerJechowetal.2014, author = {Zink, Christof and Werner, Nils and Jechow, Andreas and Heuer, Axel and Menzel, Ralf}, title = {Multi-wavelength operation of a single broad area diode laser by spectral beam combining}, series = {IEEE photonics technology letters}, volume = {26}, journal = {IEEE photonics technology letters}, number = {3}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {1041-1135}, doi = {10.1109/LPT.2013.2291963}, pages = {253 -- 256}, year = {2014}, abstract = {Stabilized multi-wavelength emission from a single emitter broad area diode laser (BAL) is realized by utilizing an external cavity with a spectral beam combining architecture. Self-organized emitters that are equidistantly spaced across the slow axis are enforced by the spatially distributed wavelength selectivity of the external cavity. This resulted in an array like near-field emission although the BAL is physically a single emitter without any epitaxial sub-structuring and only one electrical contact. Each of the self-organized emitters is operated at a different wavelength and the emission is multiplexed into one spatial mode with near-diffraction limited beam quality. With this setup, multi-line emission of 31 individual spectral lines centered around and a total spectral width of 3.6 nm is realized with a 1000 mu m wide BAL just above threshold. To the best of our knowledge, this is the first demonstration of such a self-organization of emitters by optical feedback utilizing a spectral beam combining architecture.}, language = {en} } @article{ArcherBarnackaBeilickeetal.2014, author = {Archer, A. and Barnacka, Anna and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Biteau, Jonathan and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, W. and Chen, Xiaoming and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Galante, N. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hakansson, Nils and Hanna, D. and Holder, J. and Hughes, G. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Kumar, S. and Lang, M. J. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, Manuela and Popkow, A. and Prokoph, H. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zajczyk, A. and Zitzer, B.}, title = {Very-high energy observations of the galactic center region by veritas IN 2010-2012}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {790}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/790/2/149}, pages = {9}, year = {2014}, abstract = {The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) gamma-ray observations. Potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g., Sgr A East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above similar to 2.5 TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic, and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models.}, language = {en} } @article{ZinkNiebuhrJechowetal.2014, author = {Zink, Christof and Niebuhr, Mario and Jechow, Andreas and Heuer, Axel and Menzel, Ralf}, title = {Broad area diode laser with on-chip transverse Bragg grating stabilized in an off-axis external cavity}, series = {Optics express : the international electronic journal of optics}, volume = {22}, journal = {Optics express : the international electronic journal of optics}, number = {12}, publisher = {Optical Society of America}, address = {Washington}, issn = {1094-4087}, doi = {10.1364/OE.22.014108}, pages = {14108 -- 14113}, year = {2014}, abstract = {The emission characteristics of a novel, specially designed broad area diode laser (BAL) with on-chip transversal Bragg resonance (TBR) grating in lateral direction were investigated in an off-axis external cavity setup. The internal TBR grating defines a low loss transversal mode at a specific angle of incidence and a certain wavelength. By providing feedback at this specific angle with an external mirror, it is possible to select this low loss transverse mode and stabilize the BAL. Near diffraction limited emission with an almost single lobed far field pattern could be realized, in contrast to the double lobed far field pattern of similar setups using standard BALs or phase-locked diode laser arrays. Furthermore, we could achieve a narrow bandwidth emission with a simplified setup without external frequency selective elements. (C) 2014 Optical Society of America}, language = {en} } @misc{CardinalettiKestersBerthoetal.2014, author = {Cardinaletti, Ilaria and Kesters, Jurgen and Bertho, Sabine and Conings, Bert and Piersimoni, Fortunato and Lutsen, Laurence and Nesladek, Milos and Van Mele, Bruno and Van Assche, Guy and Vandewal, Koen and Salleo, Alberto and Vanderzande, Dirk and Maes, Wouter and Manca, Jean V.}, title = {Toward bulk heterojunction polymer solar cells with thermally stable active layer morphology}, series = {Journal of photonics for energy}, volume = {4}, journal = {Journal of photonics for energy}, publisher = {SPIE}, address = {Bellingham}, issn = {1947-7988}, doi = {10.1117/1.JPE.4.040997}, pages = {12}, year = {2014}, abstract = {When state-of-the-art bulk heterojunction organic solar cells with ideal morphology are exposed to prolonged storage or operation at elevated temperatures, a thermally induced disruption of the active layer blend can occur, in the form of a separation of donor and acceptor domains, leading to diminished photovoltaic performance. Toward the long-term use of organic solar cells in real-life conditions, an important challenge is, therefore, the development of devices with a thermally stable active layer morphology. Several routes are being explored, ranging from the use of high glass transition temperature, cross-linkable and/or side-chain functionalized donor and acceptor materials, to light-induced dimerization of the fullerene acceptor. A better fundamental understanding of the nature and underlying mechanisms of the phase separation and stabilization effects has been obtained through a variety of analytical, thermal analysis, and electro-optical techniques. Accelerated aging systems have been used to study the degradation kinetics of bulk heterojunction solar cells in situ at various temperatures to obtain aging models predicting solar cell lifetime. The following contribution gives an overview of the current insights regarding the intrinsic thermally induced aging effects and the proposed solutions, illustrated by examples of our own research groups. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.}, language = {en} } @article{ChengDingZhangetal.2014, author = {Cheng, X. and Ding, M. D. and Zhang, J. and Sun, X. D. and Guo, Y. and Wang, Yi-Ming and Kliem, Bernhard and Deng, Y. Y.}, title = {Formation of a double-decker magnetic flux rope in the sigmoidal solar active region 11520}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {789}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/789/2/93}, pages = {12}, year = {2014}, abstract = {In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s(-1). The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.}, language = {en} } @article{BeshnovaCherstvyVainshteinetal.2014, author = {Beshnova, Daria A. and Cherstvy, Andrey G. and Vainshtein, Yevhen and Teif, Vladimir B.}, title = {Regulation of the nucleosome repeat length in vivo by the DNA sequence, protein concentrations and long-range interactions}, series = {PLoS Computational Biology : a new community journal}, volume = {10}, journal = {PLoS Computational Biology : a new community journal}, number = {7}, publisher = {PLoS}, address = {San Fransisco}, issn = {1553-734X}, doi = {10.1371/journal.pcbi.1003698}, pages = {14}, year = {2014}, abstract = {The nucleosome repeat length (NRL) is an integral chromatin property important for its biological functions. Recent experiments revealed several conflicting trends of the NRL dependence on the concentrations of histones and other architectural chromatin proteins, both in vitro and in vivo, but a systematic theoretical description of NRL as a function of DNA sequence and epigenetic determinants is currently lacking. To address this problem, we have performed an integrative biophysical and bioinformatics analysis in species ranging from yeast to frog to mouse where NRL was studied as a function of various parameters. We show that in simple eukaryotes such as yeast, a lower limit for the NRL value exists, determined by internucleosome interactions and remodeler action. For higher eukaryotes, also the upper limit exists since NRL is an increasing but saturating function of the linker histone concentration. Counterintuitively, smaller H1 variants or non-histone architectural proteins can initiate larger effects on the NRL due to entropic reasons. Furthermore, we demonstrate that different regimes of the NRL dependence on histone concentrations exist depending on whether DNA sequence-specific effects dominate over boundary effects or vice versa. We consider several classes of genomic regions with apparently different regimes of the NRL variation. As one extreme, our analysis reveals that the period of oscillations of the nucleosome density around bound RNA polymerase coincides with the period of oscillations of positioning sites of the corresponding DNA sequence. At another extreme, we show that although mouse major satellite repeats intrinsically encode well-defined nucleosome preferences, they have no unique nucleosome arrangement and can undergo a switch between two distinct types of nucleosome positioning.}, language = {en} } @article{GaoWangLinetal.2014, author = {Gao, Guan-Nan and Wang, Min and Lin, Jun and Wu, Ning and Tan, Cheng-Ming and Kliem, Bernhard and Su, Yang}, title = {Radio observations of the fine structure inside a post-CME current sheet}, series = {Research in astronomy and astrophysics : a publication of the Chinese Astronomical Society and National Astronomical Observatories, Chinese Academy of Sciences}, volume = {14}, journal = {Research in astronomy and astrophysics : a publication of the Chinese Astronomical Society and National Astronomical Observatories, Chinese Academy of Sciences}, number = {7}, publisher = {Chinese Astronomical Society and National Astronomical Observatories, Chinese Academy of Sciences}, address = {Beijing}, issn = {1674-4527}, doi = {10.1088/1674-4527/14/7/006}, pages = {843 -- 854}, year = {2014}, abstract = {A solar radio burst was observed in a coronal mass ejection/flare event by the Solar Broadband Radio Spectrometer at the Huairou Solar Observing Station on 2004 December 1. The data exhibited various patterns of plasma motions, suggestive of the interaction between sunward moving plasmoids and the flare loop system during the impulsive phase of the event. In addition to the radio data, the associated white-light, H alpha, extreme ultraviolet light, and soft and hard X-rays were also studied.}, language = {en} } @article{KliemLinForbesetal.2014, author = {Kliem, Bernhard and Lin, J. and Forbes, T. G. and Priest, E. R. and Toeroek, T.}, title = {Catastrophe versus instability for the eruption of a toroadal solar magnetic flux}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {789}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/789/1/46}, pages = {13}, year = {2014}, abstract = {The onset of a solar eruption is formulated here as either a magnetic catastrophe or as an instability. Both start with the same equation of force balance governing the underlying equilibria. Using a toroidal flux rope in an external bipolar or quadrupolar field as a model for the current-carrying flux, we demonstrate the occurrence of a fold catastrophe by loss of equilibrium for several representative evolutionary sequences in the stable domain of parameter space. We verify that this catastrophe and the torus instability occur at the same point; they are thus equivalent descriptions for the onset condition of solar eruptions.}, language = {en} } @article{ZhangChenBoettcher2014, author = {Zhang, Haocheng and Chen, Xuhui and Boettcher, Markus}, title = {Synchrotron polarization in blazars}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {789}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/789/1/66}, pages = {16}, year = {2014}, abstract = {We present a detailed analysis of time-and energy-dependent synchrotron polarization signatures in a shock-in-jet model for gamma-ray blazars. Our calculations employ a full three-dimensional radiation transfer code, assuming a helical magnetic field throughout the jet. The code considers synchrotron emission from an ordered magnetic field, and takes into account all light-travel-time and other relevant geometric effects, while the relevant synchrotron self-Compton and external Compton effects are handled with the two-dimensional Monte-Carlo/Fokker-Planck (MCFP) code. We consider several possible mechanisms through which a relativistic shock propagating through the jet may affect the jet plasma to produce a synchrotron and high-energy flare. Most plausibly, the shock is expected to lead to a compression of the magnetic field, increasing the toroidal field component and thereby changing the direction of the magnetic field in the region affected by the shock. We find that such a scenario leads to correlated synchrotron + synchrotron-self-Compton flaring, associated with substantial variability in the synchrotron polarization percentage and position angle. Most importantly, this scenario naturally explains large polarization angle rotations by greater than or similar to 180 degrees, as observed in connection with gamma-ray flares in several blazars, without the need for bent or helical jet trajectories or other nonaxisymmetric jet features.}, language = {en} } @article{CherstvyMetzler2014, author = {Cherstvy, Andrey G. and Metzler, Ralf}, title = {Nonergodicity, fluctuations, and criticality in heterogeneous diffusion processes}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {90}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {1}, publisher = {American Physical Society}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.90.012134}, pages = {11}, year = {2014}, abstract = {We study the stochastic behavior of heterogeneous diffusion processes with the power-law dependence D(x) similar to vertical bar x vertical bar(alpha) of the generalized diffusion coefficient encompassing sub- and superdiffusive anomalous diffusion. Based on statistical measures such as the amplitude scatter of the time-averaged mean-squared displacement of individual realizations, the ergodicity breaking and non-Gaussianity parameters, as well as the probability density function P(x, t), we analyze the weakly nonergodic character of the heterogeneous diffusion process and, particularly, the degree of irreproducibility of individual realizations. As we show, the fluctuations between individual realizations increase with growing modulus vertical bar alpha vertical bar of the scaling exponent. The fluctuations appear to diverge when the critical value alpha = 2 is approached, while for even larger alpha the fluctuations decrease, again. At criticality, the power-law behavior of the mean-squared displacement changes to an exponentially fast growth, and the fluctuations of the time-averaged mean-squared displacement do not converge for increasing number of realizations. From a systematic comparison we observe some striking similarities of the heterogeneous diffusion process with the familiar subdiffusive continuous time random walk process with power-law waiting time distribution and diverging characteristic waiting time.}, language = {en} } @article{ReibisVoellerGittetal.2014, author = {Reibis, Rona Katharina and V{\"o}ller, Heinz and Gitt, Anselm and Jannowitz, Christina and Halle, Martin and Pittrow, David and Hildemann, Steven}, title = {Management of patients with ST- segment elevation or non- ST- segment elevation acute coronary syndromes in cardiac rehabilitation centers}, series = {Clinical cardiology : international journal for cardiovascular diseases}, volume = {37}, journal = {Clinical cardiology : international journal for cardiovascular diseases}, number = {4}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0160-9289}, doi = {10.1002/clc.22241}, pages = {213 -- 221}, year = {2014}, abstract = {BackgroundCurrent data on the management of patients in cardiac rehabilitation (CR) after an acute hospital stay due to ST-segment elevation or non-ST segment elevation acute coronary syndromes (STE-ACS or NSTE-ACS) are limited. We aimed to describe patient characteristics, risk factor management, and lipid target achievement of patients in CR in Germany and compare the 2 groups. HypothesisWith respect to the risk factor pattern and treatment effects during a CR stay, there are important differences between STE-ACS and NSTE-ACS patients. MethodsComparison of 7950 patients by STE-ACS or NSTE-ACS status in the Transparency Registry to Objectify Guideline-Oriented Risk Factor Management registry (2010) who underwent an inpatient CR period of about 3 weeks. ResultsSTE-ACS patients compared to NSTE-ACS patients were significantly younger (60.5 vs 64.4 years, P < 0.0001), and had diabetes mellitus, hypertension, or any risk factor (exception: smoking) less often. At discharge, in STE-ACS compared to NSTE-ACS patients, the low-density lipoprotein cholesterol (LDL-C) <100 mg/dL goal was achieved by 75.3\% and 76.2\%, respectively (LDL-C <70 mg/dL by 27.7\% and 27.4\%), the high-density lipoprotein cholesterol goal of >50 mg/dL in women and >40 mg/dL in men was achieved by 49.3\% and 49.0\%, respectively, and the triglycerides goal of <150 mg/dl was achievedby 72.3\% and 74.3\%, respectively (all comparisons not significant). Mean systolic and diastolic blood pressure were 121/74 and 123/74 mm Hg, respectively (P < 0.0001 systolic, diastolic not significant). The maximum exercise capacity was 110 and 102 W, respectively (P < 0.0001), and the maximum walking distance was 581 and 451 meters, respectively (P value not significant). ConclusionsPatients with STE-ACS and NSTE-ACS differed moderately in their baseline characteristics. Both groups benefited from the participation in CR, as their lipid profile, blood pressure, and physical fitness improved.}, language = {en} } @article{GoychukKharchenkoMetzler2014, author = {Goychuk, Igor and Kharchenko, Vasyl O. and Metzler, Ralf}, title = {How Molecular Motors Work in the Crowded Environment of Living Cells: Coexistence and Efficiency of Normal and Anomalous Transport}, series = {PLoS one}, volume = {9}, journal = {PLoS one}, number = {3}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0091700}, pages = {7}, year = {2014}, abstract = {Recent experiments reveal both passive subdiffusion of various nanoparticles and anomalous active transport of such particles by molecular motors in the molecularly crowded environment of living biological cells. Passive and active microrheology reveals that the origin of this anomalous dynamics is due to the viscoelasticity of the intracellular fluid. How do molecular motors perform in such a highly viscous, dissipative environment? Can we explain the observed co-existence of the anomalous transport of relatively large particles of 100 to 500 nm in size by kinesin motors with the normal transport of smaller particles by the same molecular motors? What is the efficiency of molecular motors in the anomalous transport regime? Here we answer these seemingly conflicting questions and consistently explain experimental findings in a generalization of the well-known continuous diffusion model for molecular motors with two conformational states in which viscoelastic effects are included.}, language = {en} } @article{SchulzBarkaiMetzler2014, author = {Schulz, Johannes H. P. and Barkai, Eli and Metzler, Ralf}, title = {Aging renewal theory and application to random walks}, series = {Physical review : X, Expanding access}, volume = {4}, journal = {Physical review : X, Expanding access}, number = {1}, publisher = {American Physical Society}, address = {College Park}, issn = {2160-3308}, doi = {10.1103/PhysRevX.4.011028}, pages = {24}, year = {2014}, abstract = {We discuss a renewal process in which successive events are separated by scale-free waiting time periods. Among other ubiquitous long-time properties, this process exhibits aging: events counted initially in a time interval [0, t] statistically strongly differ from those observed at later times [t(a,) t(a) + t]. The versatility of renewal theory is owed to its abstract formulation. Renewals can be interpreted as steps of a random walk, switching events in two-state models, domain crossings of a random motion, etc. In complex, disordered media, processes with scale-free waiting times play a particularly prominent role. We set up a unified analytical foundation for such anomalous dynamics by discussing in detail the distribution of the aging renewal process. We analyze its half-discrete, half-continuous nature and study its aging time evolution. These results are readily used to discuss a scale-free anomalous diffusion process, the continuous-time random walk. By this, we not only shed light on the profound origins of its characteristic features, such as weak ergodicity breaking, along the way, we also add an extended discussion on aging effects. In particular, we find that the aging behavior of time and ensemble averages is conceptually very distinct, but their time scaling is identical at high ages. Finally, we show how more complex motion models are readily constructed on the basis of aging renewal dynamics.}, language = {en} } @article{PalyulinChechkinMetzler2014, author = {Palyulin, Vladimir V. and Chechkin, Aleksei V. and Metzler, Ralf}, title = {Levy flights do not always optimize random blind search for sparse targets}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {111}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {8}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1320424111}, pages = {2931 -- 2936}, year = {2014}, abstract = {It is generally believed that random search processes based on scale-free, Levy stable jump length distributions (Levy flights) optimize the search for sparse targets. Here we show that this popular search advantage is less universal than commonly assumed. We study the efficiency of a minimalist search model based on Levy flights in the absence and presence of an external drift (underwater current, atmospheric wind, a preference of the walker owing to prior experience, or a general bias in an abstract search space) based on two different optimization criteria with respect to minimal search time and search reliability (cumulative arrival probability). Although Levy flights turn out to be efficient search processes when the target is far from the starting point, or when relative to the starting point the target is upstream, we show that for close targets and for downstream target positioning regular Brownian motion turns out to be the advantageous search strategy. Contrary to claims that Levy flights with a critical exponent alpha = 1 are optimal for the search of sparse targets in different settings, based on our optimization parameters the optimal a may range in the entire interval (1, 2) and especially include Brownian motion as the overall most efficient search strategy.}, language = {en} } @article{TalukderSenChakrabortietal.2014, author = {Talukder, Srijeeta and Sen, Shrabani and Chakraborti, Prantik and Metzler, Ralf and Banik, Suman K. and Chaudhury, Pinaki}, title = {Breathing dynamics based parameter sensitivity analysis of hetero-polymeric DNA}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {140}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {12}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4869112}, pages = {10}, year = {2014}, abstract = {We study the parameter sensitivity of hetero-polymeric DNA within the purview of DNA breathing dynamics. The degree of correlation between the mean bubble size and the model parameters is estimated for this purpose for three different DNA sequences. The analysis leads us to a better understanding of the sequence dependent nature of the breathing dynamics of hetero-polymeric DNA. Out of the 14 model parameters for DNA stability in the statistical Poland-Scheraga approach, the hydrogen bond interaction epsilon(hb)(AT) for an AT base pair and the ring factor. turn out to be the most sensitive parameters. In addition, the stacking interaction epsilon(st)(TA-TA) for an TA-TA nearest neighbor pair of base-pairs is found to be the most sensitive one among all stacking interactions. Moreover, we also establish that the nature of stacking interaction has a deciding effect on the DNA breathing dynamics, not the number of times a particular stacking interaction appears in a sequence. We show that the sensitivity analysis can be used as an effective measure to guide a stochastic optimization technique to find the kinetic rate constants related to the dynamics as opposed to the case where the rate constants are measured using the conventional unbiased way of optimization. (c) 2014 AIP Publishing LLC.}, language = {en} } @unpublished{FoehlischdeGrootOdeliusetal.2014, author = {F{\"o}hlisch, Alexander and de Groot, F. M. F. and Odelius, Michael and Techert, Simone and Wernet, P.}, title = {Comment on "state-dependent electron delocalization dynamics at the solute-solvent interface: soft-x-ray absorption spectroscopy and lambda b initio calculations"}, series = {Physical review letters}, volume = {112}, journal = {Physical review letters}, number = {12}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.112.129302}, pages = {2}, year = {2014}, language = {en} } @article{AliuAuneBeheraetal.2014, author = {Aliu, E. and Aune, T. and Behera, B. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Buckley, J. H. and Bugaev, V. and Cardenzana, J. V. and Cerruti, M. and Chen, X. and Ciupik, L. and Connolly, M. P. and Cui, W. and Duke, C. and Dumm, J. and Errando, M. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Kaaret, P. and Kargaltsev, Oleg and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Lang, M. J. and Madhavan, A. S. and Maier, G. and Majumdar, P. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Pandel, D. and Perkins, J. S. and Pohl, Manuela and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Skole, C. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zitzer, B.}, title = {Observations of the unidentified gamm-ray source TeV J2032+4130 BY Veritas}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {783}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/783/1/16}, pages = {9}, year = {2014}, language = {en} } @article{MaistrenkoPenkovskyRosenblum2014, author = {Maistrenko, Yuri and Penkovsky, Bogdan and Rosenblum, Michael}, title = {Solitary state at the edge of synchrony in ensembles with attractive and repulsive interactions}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {89}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {6}, publisher = {American Physical Society}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.89.060901}, pages = {5}, year = {2014}, abstract = {We discuss the desynchronization transition in networks of globally coupled identical oscillators with attractive and repulsive interactions. We show that, if attractive and repulsive groups act in antiphase or close to that, a solitary state emerges with a single repulsive oscillator split up from the others fully synchronized. With further increase of the repulsing strength, the synchronized cluster becomes fuzzy and the dynamics is given by a variety of stationary states with zero common forcing. Intriguingly, solitary states represent the natural link between coherence and incoherence. The phenomenon is described analytically for phase oscillators with sine coupling and demonstrated numerically for more general amplitude models.}, language = {en} } @article{ZaritskyCourtoisMunozMateosetal.2014, author = {Zaritsky, Dennis and Courtois, Helene and Munoz-Mateos, Juan-Carlos and Sorce, Jenny and Erroz-Ferrer, S. and Comeron, S. and Gadotti, D. A. and Gil De Paz, A. and Hinz, J. L. and Laurikainen, E. and Kim, T. and Laine, J. and Menendez-Delmestre, K. and Mizusawa, T. and Regan, M. W. and Salo, H. and Seibert, M. and Sheth, K. and Athanassoula, E. and Bosma, A. and Cisternas, M. and Ho, Luis C. and Holwerda, B.}, title = {The baryonic Tully-Fisher relationship for S(4)G galaxies and the "condensed" baryon fraction of galaxies}, series = {The astronomical journal}, volume = {147}, journal = {The astronomical journal}, number = {6}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-6256}, doi = {10.1088/0004-6256/147/6/134}, pages = {11}, year = {2014}, abstract = {We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of Hi spectral line profiles to examine the baryonic Tully-Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully-Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which we find to be 3.5 +/- 0.2 (Delta log M-baryon/Delta log v(c)), implies that on average a nearly constant fraction (similar to 0.4) of all baryons expected to be in a halo are "condensed" onto the central region of rotationally supported galaxies. The condensed baryon fraction, M-baryon/M-total, is, to our measurement precision, nearly independent of galaxy circular velocity (our sample spans circular velocities, vc, between 60 and 250 km s(-1), but is extended to v(c) similar to 10 km s(-1) using data from the literature). The observed galaxy-to-galaxy scatter in this fraction is generally <= a factor of 2 despite fairly liberal selection criteria. These results imply that cooling and heating processes, such as cold versus hot accretion, mass loss due to stellar winds, and active galactic nucleus driven feedback, to the degree that they affect the global galactic properties involved in the BTF, are independent of halo mass for galaxies with 10 < v(c) < 250 km s(-1) and typically introduce no more than a factor of two range in the resulting M-baryon/M-total. Recent simulations by Aumer et al. of a small sample of disk galaxies are in excellent agreement with our data, suggesting that current simulations are capable of reproducing the global properties of individual disk galaxies. More detailed comparison to models using the BTF holds great promise, but awaits improved determinations of the stellar masses.}, language = {en} } @article{ShinCherstvyMetzler2014, author = {Shin, Jaeoh and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Mixing and segregation of ring polymers: spatial confinement and molecular crowding effects}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/5/053047}, pages = {19}, year = {2014}, abstract = {During the life cycle of bacterial cells the non-mixing of the two ring-shaped daughter genomes is an important prerequisite for the cell division process. Mimicking the environments inside highly crowded biological cells, we study the dynamics and statistical behavior of two flexible ring polymers in the presence of cylindrical confinement and crowding molecules. From extensive computer simulations we determine the degree of ring-ring overlap and the number of inter-monomer contacts for varying volume fractions phi of crowders. We also examine the entropic demixing of polymer rings in the presence of mobile crowders and determine the characteristic times of the internal polymer dynamics. Effects of the ring length on ring-ring overlap are also analyzed. In particular, on systematic variation of the fraction of crowding molecules, a (1 - phi)-scaling is found for the ring-ring overlap length along the cylinder axis, and a non-monotonic dependence of the 3D ring-ring contact number with a maximum at phi approximate to 0.2 is obtained. Our results demonstrate that polymer rings are demixed and separated by particular entropy-favourable partitioning of crowders along the axis of the cylindrical simulation box. These findings help to rationalize the implications of macromolecular crowding for circular DNA molecules in confined spaces inside bacteria as well as in localized cellular compartments inside eukaryotic cells.}, language = {en} } @article{MiedemaWernetFoehlisch2014, author = {Miedema, Piter S. and Wernet, Philippe and F{\"o}hlisch, Alexander}, title = {State-dependent fluorescence yields through the core-valence Coulomb exchange parameter}, series = {Physical review : A, Atomic, molecular, and optical physics}, volume = {89}, journal = {Physical review : A, Atomic, molecular, and optical physics}, number = {5}, publisher = {American Physical Society}, address = {College Park}, issn = {1050-2947}, doi = {10.1103/PhysRevA.89.052507}, pages = {7}, year = {2014}, abstract = {Total and partial fluorescence yield (PFY) L-edge x-ray absorption spectra differ from the transmission x-ray absorption spectra (XAS) through state-dependent fluorescence yield across the XAS. For 3d(1) to 3d(9) in octahedral symmetry we apply simulations of PFY and XAS and show how the atomic 2p3d Coulomb exchange parameter G(pd) governs the differences in the L-3/(L-2 + L-3) branching ratio between PFY and XAS. G(pd) orders the XAS final states following Hund's rules creating a strong state-dependent fluorescence decay strength variation across the XAS leading to the differences between PFY and XAS.}, language = {en} } @article{Mulansky2014, author = {Mulansky, Mario}, title = {Scaling of chaos in strongly nonlinear lattices}, series = {Chaos : an interdisciplinary journal of nonlinear science}, volume = {24}, journal = {Chaos : an interdisciplinary journal of nonlinear science}, number = {2}, publisher = {American Institute of Physics}, address = {Melville}, issn = {1054-1500}, doi = {10.1063/1.4868259}, pages = {6}, year = {2014}, abstract = {Although it is now understood that chaos in complex classical systems is the foundation of thermodynamic behavior, the detailed relations between the microscopic properties of the chaotic dynamics and the macroscopic thermodynamic observations still remain mostly in the dark. In this work, we numerically analyze the probability of chaos in strongly nonlinear Hamiltonian systems and find different scaling properties depending on the nonlinear structure of the model. We argue that these different scaling laws of chaos have definite consequences for the macroscopic diffusive behavior, as chaos is the microscopic mechanism of diffusion. This is compared with previous results on chaotic diffusion [M. Mulansky and A. Pikovsky, New J. Phys. 15, 053015 (2013)], and a relation between microscopic chaos and macroscopic diffusion is established. (C) 2014 AIP Publishing LLC.}, language = {en} } @article{AliuArchambaultArlenetal.2014, author = {Aliu, E. and Archambault, S. and Arlen, T. and Aune, T. and Barnacka, Anna and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Cerruti, M. and Chen, X. and Ciupik, L. and Collins-Hughes, E. and Connolly, M. P. and Cui, W. and Dumm, J. and Eisch, J. D. and Falcone, A. and Federici, S. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hakansson, N. and Hanna, D. and Holder, J. and Hughes, G. and Hughes, Z. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Lang, M. J. and Madhavan, A. S. and Majumdar, P. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Mukherjee, R. and Nelson, T. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, M. and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sadun, A. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Sheidaei, F. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Tyler, J. and Varlotta, A. and Vassiliev, V. V. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zitzer, B. and Boettcher, Markus and Fumagalli, M.}, title = {Investigating broadband variability of the TeV blazar 1ES 1959+650}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {797}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {Veritas Collaboration}, issn = {0004-637X}, doi = {10.1088/0004-637X/797/2/89}, pages = {11}, year = {2014}, abstract = {We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift Ultraviolet and Optical Telescope, X-ray observations by the Swift X-ray Telescope, high-energy gamma-ray observations with the Fermi Large Area Telescope, and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 2012 April 17 and 2012 June 1 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66\% of the Crab Nebula flux, observed on a single night during the observation period, the reflected emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV.}, language = {en} } @article{MeierKriegelMotschmannetal.2014, author = {Meier, Patrick and Kriegel, Hendrik and Motschmann, Uwe and Schmidt, J{\"u}rgen and Spahn, Frank and Hill, Thomas W. and Dong, Yaxue and Jones, Geraint H.}, title = {A model of the spatial and size distribution of Enceladus' dust plume}, series = {Planetary and space science}, volume = {104}, journal = {Planetary and space science}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2014.09.016}, pages = {216 -- 233}, year = {2014}, language = {en} } @article{MiedemaBeyeKoenneckeetal.2014, author = {Miedema, Piter Sybren and Beye, Martin and Koennecke, R. and Schiwietz, Gregor and F{\"o}hlisch, Alexander}, title = {Thermal evolution of the band edges of 6H-SiC: X-ray methods compared to the optical band gap}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {197}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2014.08.003}, pages = {37 -- 42}, year = {2014}, abstract = {The band gap of semiconductors like silicon and silicon carbide (SIC) is the key for their device properties. In this research, the band gap of 6H-SiC and its temperature dependence were analyzed with silicon 2p X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) allowing for a separate analysis of the conduction-band minimum (CBM) and valence-band maximum (VBM) components of the band gap. The temperature-dependent asymmetric band gap shrinking of 6H-SiC was determined with a valence-band slope of +2.45 x 10(-4) eV/K and a conduction-band slope of -1.334 x 10(-4) eV/K. The apparent asymmetry, e.g., that two thirds of the band-gap shrinking with increasing temperature is due to the VBM evolution in 6H-SiC, is similar to the asymmetry obtained for pure silicon before. The overall band gap temperature-dependence determined with XAS and nonresonant XES is compared to temperature-dependent optical studies. The core-excitonic binding energy appearing in the Si 2p XAS is extracted as the main difference. In addition, the energy loss of the onset of the first band in RIXS yields to values similar to the optical band gap over the tested temperature range. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{TobieTeanbyCoustenisetal.2014, author = {Tobie, G. and Teanby, N. A. and Coustenis, A. and Jaumann, Ralf and Raulin, E. and Schmidt, J. and Carrasco, N. and Coates, Andrew J. and Cordier, D. and De Kok, R. and Geppert, W. D. and Lebreton, J. -P. and Lefevre, A. and Livengood, T. A. and Mandt, K. E. and Mitri, G. and Nimmo, F. and Nixon, C. A. and Norman, L. and Pappalardo, R. T. and Postberg, F. and Rodriguez, S. and SchuizeMakuch, D. and Soderblom, J. M. and Solomonidou, A. and Stephan, K. and Stofan, E. R. and Turtle, E. P. and Wagner, R. J. and West, R. A. and Westlake, J. H.}, title = {Science goals and mission concept for the future exploration of Titan and Enceladus}, series = {Planetary and space science}, volume = {104}, journal = {Planetary and space science}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2014.10.002}, pages = {59 -- 77}, year = {2014}, language = {en} } @article{ArridgeAchilleosAgarwaletal.2014, author = {Arridge, Christopher S. and Achilleos, N. and Agarwal, Jessica and Agnor, C. B. and Ambrosi, R. and Andre, N. and Badman, S. V. and Baines, K. and Banfield, D. and Barthelemy, M. and Bisi, M. M. and Blum, J. and Bocanegra-Bahamon, T. and Bonfond, B. and Bracken, C. and Brandt, P. and Briand, C. and Briois, C. and Brooks, S. and Castillo-Rogez, J. and Cavalie, T. and Christophe, B. and Coates, Andrew J. and Collinson, G. and Cooper, J. F. and Costa-Sitja, M. and Courtin, R. and Daglis, I. A. and De Pater, Imke and Desai, M. and Dirkx, D. and Dougherty, M. K. and Ebert, R. W. and Filacchione, Gianrico and Fletcher, Leigh N. and Fortney, J. and Gerth, I. and Grassi, D. and Grodent, D. and Gr{\"u}n, Eberhard and Gustin, J. and Hedman, M. and Helled, R. and Henri, P. and Hess, Sebastien and Hillier, J. K. and Hofstadter, M. H. and Holme, R. and Horanyi, M. and Hospodarsky, George B. and Hsu, S. and Irwin, P. and Jackman, C. M. and Karatekin, O. and Kempf, Sascha and Khalisi, E. and Konstantinidis, K. and Kruger, H. and Kurth, William S. and Labrianidis, C. and Lainey, V. and Lamy, L. L. and Laneuville, Matthieu and Lucchesi, D. and Luntzer, A. and MacArthur, J. and Maier, A. and Masters, A. and McKenna-Lawlor, S. and Melin, H. and Milillo, A. and Moragas-Klostermeyer, Georg and Morschhauser, Achim and Moses, J. I. and Mousis, O. and Nettelmann, N. and Neubauer, F. M. and Nordheim, T. and Noyelles, B. and Orton, G. S. and Owens, Mathew and Peron, R. and Plainaki, C. and Postberg, F. and Rambaux, N. and Retherford, K. and Reynaud, Serge and Roussos, E. and Russell, C. T. and Rymer, Am. and Sallantin, R. and Sanchez-Lavega, A. and Santolik, O. and Saur, J. and Sayanagi, Km. and Schenk, P. and Schubert, J. and Sergis, N. and Sittler, E. C. and Smith, A. and Spahn, Frank and Srama, Ralf and Stallard, T. and Sterken, V. and Sternovsky, Zoltan and Tiscareno, M. and Tobie, G. and Tosi, F. and Trieloff, M. and Turrini, D. and Turtle, E. P. and Vinatier, S. and Wilson, R. and Zarkat, P.}, title = {The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets}, series = {Planetary and space science}, volume = {104}, journal = {Planetary and space science}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2014.08.009}, pages = {122 -- 140}, year = {2014}, abstract = {Giant planets helped to shape the conditions we see in the Solar System today and they account for more than 99\% of the mass of the Sun's planetary system. They can be subdivided into the Ice Giants (Uranus and Neptune) and the Gas Giants (Jupiter and Saturn), which differ from each other in a number of fundamental ways. Uranus, in particular is the most challenging to our understanding of planetary formation and evolution, with its large obliquity, low self-luminosity, highly asymmetrical internal field, and puzzling internal structure. Uranus also has a rich planetary system consisting of a system of inner natural satellites and complex ring system, five major natural icy satellites, a system of irregular moons with varied dynamical histories, and a highly asymmetrical magnetosphere. Voyager 2 is the only spacecraft to have explored Uranus, with a flyby in 1986, and no mission is currently planned to this enigmatic system. However, a mission to the uranian system would open a new window on the origin and evolution of the Solar System and would provide crucial information on a wide variety of physicochemical processes in our Solar System. These have clear implications for understanding exoplanetary systems. In this paper we describe the science case for an orbital mission to Uranus with an atmospheric entry probe to sample the composition and atmospheric physics in Uranus' atmosphere. The characteristics of such an orbiter and a strawman scientific payload are described and we discuss the technical challenges for such a mission. This paper is based on a white paper submitted to the European Space Agency's call for science themes for its large-class mission programme in 2013.}, language = {en} } @article{GodecChechkinBarkaietal.2014, author = {Godec, Aljaz and Chechkin, Aleksei V. and Barkai, Eli and Kantz, Holger and Metzler, Ralf}, title = {Localisation and universal fluctuations in ultraslow diffusion processes}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {47}, journal = {Journal of physics : A, Mathematical and theoretical}, number = {49}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8113/47/49/492002}, pages = {10}, year = {2014}, abstract = {We study ultraslow diffusion processes with logarithmic mean squared displacement (MSD) < x(2)(t)> similar or equal to log(gamma)t. Comparison of annealed (renewal) continuous time random walks (CTRWs) with logarithmic waiting time distribution psi(tau) similar or equal to 1/(tau log(1+gamma)tau) and Sinai diffusion in quenched random landscapes reveals striking similarities, despite the great differences in their physical nature. In particular, they exhibit a weakly non-ergodic disparity of the time-averaged and ensemble-averaged MSDs. Remarkably, for the CTRW we observe that the fluctuations of time averages become universal, with an exponential suppression of mobile trajectories. We discuss the fundamental connection between the Golosov localization effect and non-ergodicity in the sense of the disparity between ensemble-averaged MSD and time-averaged MSD.}, language = {en} } @article{NagelGuvenThevesetal.2014, author = {Nagel, Oliver and Guven, Can and Theves, Matthias and Driscoll, Meghan and Losert, Wolfgang and Beta, Carsten}, title = {Geometry-driven polarity in motile amoeboid cells}, series = {PLoS one}, volume = {9}, journal = {PLoS one}, number = {12}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0113382}, pages = {20}, year = {2014}, abstract = {Motile eukaryotic cells, such as leukocytes, cancer cells, and amoeba, typically move inside the narrow interstitial spacings of tissue or soil. While most of our knowledge of actin-driven eukaryotic motility was obtained from cells that move on planar open surfaces, recent work has demonstrated that confinement can lead to strongly altered motile behavior. Here, we report experimental evidence that motile amoeboid cells undergo a spontaneous symmetry breaking in confined interstitial spaces. Inside narrow channels, the cells switch to a highly persistent, unidirectional mode of motion, moving at a constant speed along the channel. They remain in contact with the two opposing channel side walls and alternate protrusions of their leading edge near each wall. Their actin cytoskeleton exhibits a characteristic arrangement that is dominated by dense, stationary actin foci at the side walls, in conjunction with less dense dynamic regions at the leading edge. Our experimental findings can be explained based on an excitable network model that accounts for the confinement-induced symmetry breaking and correctly recovers the spatio-temporal pattern of protrusions at the leading edge. Since motile cells typically live in the narrow interstitial spacings of tissue or soil, we expect that the geometry-driven polarity we report here plays an important role for movement of cells in their natural environment.}, language = {en} } @article{CherstvyChechkinMetzler2014, author = {Cherstvy, Andrey G. and Chechkin, Aleksei V. and Metzler, Ralf}, title = {Ageing and confinement in non-ergodic heterogeneous diffusion processes}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {47}, journal = {Journal of physics : A, Mathematical and theoretical}, number = {48}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8113/47/48/485002}, pages = {18}, year = {2014}, abstract = {We study the effects of ageing-the time delay between initiation of the physical process at t = 0 and start of observation at some time t(a) > 0-and spatial confinement on the properties of heterogeneous diffusion processes (HDPs) with deterministic power-law space-dependent diffusivities, D(x) = D-0 vertical bar x vertical bar(alpha). From analysis of the ensemble and time averaged mean squared displacements and the ergodicity breaking parameter quantifying the inherent degree of irreproducibility of individual realizations of the HDP we obtain striking similarities to ageing subdiffusive continuous time random walks with scale-free waiting time distributions. We also explore how both processes can be distinguished. For confined HDPs we study the long-time saturation of the ensemble and time averaged particle displacements as well as the magnitude of the inherent scatter of time averaged displacements and contrast the outcomes to the results known for other anomalous diffusion processes under confinement.}, language = {en} } @article{BeimGraben2014, author = {Beim Graben, Peter}, title = {Contextual emergence of intentionality}, series = {Journal of consciousness studies : controversies in science \& the humanities ; an international multi-disciplinary journal}, volume = {21}, journal = {Journal of consciousness studies : controversies in science \& the humanities ; an international multi-disciplinary journal}, number = {5-6}, publisher = {Imprint Academic}, address = {Exeter}, issn = {1355-8250}, pages = {75 -- 96}, year = {2014}, abstract = {By means of an intriguing physical example, magnetic surface swimmers, that can be described in terms of Dennett's intentional stance, I reconstruct a hierarchy of necessary and sufficient conditions for the applicability of the intentional strategy. It turns out that the different levels of the intentional hierarchy are contextually emergent from their respective subjacent levels by imposing stability constraints upon them. At the lowest level of the hierarchy, phenomenal physical laws emerge for the coarse-grained description of open, nonlinear, and dissipative non-equilibrium systems in critical states. One level higher, dynamic patterns, such as, for example, magnetic surface swimmers, are contextually emergent as they are invariant under certain symmetry operations. Again one level up, these patterns behave apparently rationally by selecting optimal pathways for the dissipation of energy that is delivered by external gradients. This is in accordance with the restated Second Law of thermodynamics as a stability criterion. At the highest level, true believers are intentional systems that are stable under exchanging their observation conditions.}, language = {en} } @article{HolldackOvsyannikovKuskeetal.2014, author = {Holldack, Karsten and Ovsyannikov, Ruslan and Kuske, P. and Mueller, R. and Schaelicke, A. and Scheer, M. and Gorgoi, Mihaela and Kuehn, D. and Leitner, T. and Svensson, S. and Martensson, N. and F{\"o}hlisch, Alexander}, title = {Single bunch X-ray pulses on demand from a multi-bunch synchrotron radiation source}, series = {Nature Communications}, volume = {5}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms5010}, pages = {7}, year = {2014}, abstract = {Synchrotron radiation facilities routinely operate in a multi-bunch regime, but applications relying on time-of-flight schemes require single bunch operation. Here we show that pulse picking by resonant excitation in a storage ring creates in addition to the multi-bunch operation a distinct and separable single bunch soft X-ray source. It has variable polarization, a photon flux of up to 10(7)-10(9) ph s(-1)/0.1\%BW at purity values of 10(4)-10(2) and a repetition rate of 1.25 MHz. The quasi-resonant excitation of incoherent betatron oscillations of electrons allows horizontal pulse separation at variable (also circular) polarization accessible for both, regular 30 ps pulses and ultrashort pulses of 2-3 ps duration. Combined with a new generation of angularly resolving electron spectrometers this creates unique opportunities for time-resolved photoemission studies as confirmed by time-of-flight spectra. Our pulse picking scheme is particularly suited for surface physics at diffraction-limited light sources promising ultimate spectral resolution.}, language = {en} } @article{ShinCherstvyMetzler2014, author = {Shin, Jaeoh and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Sensing viruses by mechanical tension of DNA in responsive hydrogels}, series = {Physical review : X, Expanding access}, volume = {4}, journal = {Physical review : X, Expanding access}, number = {2}, publisher = {American Physical Society}, address = {College Park}, issn = {2160-3308}, doi = {10.1103/PhysRevX.4.021002}, pages = {13}, year = {2014}, abstract = {The rapid worldwide spread of severe viral infections, often involving novel mutations of viruses, poses major challenges to our health-care systems. This means that tools that can efficiently and specifically diagnose viruses are much needed. To be relevant for broad applications in local health-care centers, such tools should be relatively cheap and easy to use. In this paper, we discuss the biophysical potential for the macroscopic detection of viruses based on the induction of a mechanical stress in a bundle of prestretched DNA molecules upon binding of viruses to the DNA. We show that the affinity of the DNA to the charged virus surface induces a local melting of the double helix into two single-stranded DNA. This process effects a mechanical stress along the DNA chains leading to an overall contraction of the DNA. Our results suggest that when such DNA bundles are incorporated in a supporting matrix such as a responsive hydrogel, the presence of viruses may indeed lead to a significant, macroscopic mechanical deformation of the matrix. We discuss the biophysical basis for this effect and characterize the physical properties of the associated DNA melting transition. In particular, we reveal several scaling relations between the relevant physical parameters of the system. We promote this DNA-based assay as a possible tool for efficient and specific virus screening.}, language = {en} } @article{Cherstvy2014, author = {Cherstvy, Andrey G.}, title = {Electrostatics and charge regulation in polyelectrolyte multi layered assembly}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {118}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {17}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp502460v}, pages = {4552 -- 4560}, year = {2014}, abstract = {We examine the implications of electrostatic interactions on formation of polyelectrolyte multilayers, in application to field-effect based biosensors for label-free detection of charged macromolecules. We present a quantitative model to describe the experimental potentiometric observations and discuss its possibilities and limitations for detection of polyelectrolyte adsorption. We examine the influence of the ionic strength and pH on the sensor response upon polyelectrolyte layer-by-layer formation. The magnitude of potential oscillations on the sensor-electrolyte interface predicted upon repetitive adsorption charge-alternating polymers agrees satisfactorily with experimental results. The model accounts for different screening by mobile ions in electrolyte and inside tightly interdigitated multilayered structure. In particular, we show that sensors' potential oscillations are larger and more persistent at lower salt conditions, while they decay faster with the number of layers at higher salt conditions, in agreement with experiments. The effects of polyelectrolyte layer thickness, substrate potential, and charge regulation on the sensor surface triggered by layer-by-layer deposition are also analyzed.}, language = {en} } @article{KruesemannGodecMetzler2014, author = {Kr{\"u}semann, Henning and Godec, Aljaz and Metzler, Ralf}, title = {First-passage statistics for aging diffusion in systems with annealed and quenched disorder}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {89}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {4}, publisher = {American Physical Society}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.89.040101}, pages = {5}, year = {2014}, abstract = {Aging, the dependence of the dynamics of a physical process on the time t(a) since its original preparation, is observed in systems ranging from the motion of charge carriers in amorphous semiconductors over the blinking dynamics of quantum dots to the tracer dispersion in living biological cells. Here we study the effects of aging on one of the most fundamental properties of a stochastic process, the first-passage dynamics. We find that for an aging continuous time random walk process, the scaling exponent of the density of first-passage times changes twice as the aging progresses and reveals an intermediate scaling regime. The first-passage dynamics depends on t(a) differently for intermediate and strong aging. Similar crossovers are obtained for the first-passage dynamics for a confined and driven particle. Comparison to the motion of an aged particle in the quenched trap model with a bias shows excellent agreement with our analytical findings. Our results demonstrate how first-passage measurements can be used to unravel the age t(a) of a physical system.}, language = {en} } @article{HarrisMellinger2014, author = {Harris, Scott and Mellinger, Axel}, title = {Towards a better understanding of dielectric barrier discharges in ferroelectrets: Paschen breakdown fields in micrometer sized voids}, series = {Journal of applied physics}, volume = {115}, journal = {Journal of applied physics}, number = {16}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-8979}, doi = {10.1063/1.4871678}, pages = {5}, year = {2014}, abstract = {Charged cellular polypropylene foams (i.e., ferro-or piezoelectrets) demonstrate high piezoelectric activity upon being electrically charged. When an external electric field is applied, dielectric barrier discharges (DBDs) occur, resulting in a separation of charges which are subsequently deposited on dielectric surfaces of internal micrometer sized voids. This deposited space charge is responsible for the piezoelectric activity of the material. Previous studies have indicated charging fields larger than predicted by Townsend's model of Paschen breakdown applied to a multilayered electromechanical model; a discrepancy which prompted the present study. The actual breakdown fields for micrometer sized voids were determined by constructing single cell voids using polypropylene spacers with heights ranging from 8 to 75 mu m, "sandwiched" between two polypropylene dielectric barriers and glass slides with semi-transparent electrodes. Subsequently, a bipolar triangular charging waveform with a peak voltage of 6 kV was applied to the samples. The breakdown fields were determined by monitoring the emission of light due to the onset of DBDs using an electron multiplying CCD camera. The breakdown fields at absolute pressures from 101 to 251 kPa were found to be in good agreement with the standard Paschen curves. Additionally, the magnitude of the light emission was found to scale linearly with the amount of gas, i.e., the height of the voids. Emissions were homogeneous over the observed regions of the voids for voids with heights of 25 lm or less and increasingly inhomogeneous for void heights greater than 40 lm at high electric fields.}, language = {en} } @misc{TalukderSenChakrabortietal.2014, author = {Talukder, Srijeeta and Sen, Shrabani and Chakraborti, Prantik and Metzler, Ralf and Banik, Suman K. and Chaudhury, Pinaki}, title = {Breathing dynamics based parameter sensitivity analysis of hetero-polymeric DNA}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {140}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {14}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4871297}, pages = {1}, year = {2014}, abstract = {We study the parameter sensitivity of hetero-polymeric DNA within the purview of DNA breathing dynamics. The degree of correlation between the mean bubble size and the model parameters is estimated for this purpose for three different DNA sequences. The analysis leads us to a better understanding of the sequence dependent nature of the breathing dynamics of hetero-polymeric DNA. Out of the 14 model parameters for DNA stability in the statistical Poland-Scheraga approach, the hydrogen bond interaction epsilon(hb)(AT) for an AT base pair and the ring factor. turn out to be the most sensitive parameters. In addition, the stacking interaction epsilon(st)(TA-TA) for an TA-TA nearest neighbor pair of base-pairs is found to be the most sensitive one among all stacking interactions. Moreover, we also establish that the nature of stacking interaction has a deciding effect on the DNA breathing dynamics, not the number of times a particular stacking interaction appears in a sequence. We show that the sensitivity analysis can be used as an effective measure to guide a stochastic optimization technique to find the kinetic rate constants related to the dynamics as opposed to the case where the rate constants are measured using the conventional unbiased way of optimization.}, language = {en} } @article{Baushev2014, author = {Baushev, Anton N.}, title = {Galaxy halo formation in the absence of violent relaxation and a universal density profile of the halo center}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {786}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/786/1/65}, pages = {8}, year = {2014}, abstract = {While N-body simulations testify to a cuspy profile of the central region of dark matter halos, observations favor a shallow, cored density profile of the central region of at least some spiral galaxies and dwarf spheroidals. We show that a central profile, very close to the observed one, inevitably forms in the center of dark matter halos if we make a supposition about a moderate energy relaxation of the system during the halo formation. If we assume the energy exchange between dark matter particles during the halo collapse is not too intensive, the profile is universal: it depends almost not at all on the properties of the initial perturbation and is very akin, but not identical, to the Einasto profile with a small Einasto index n similar to 0.5. We estimate the size of the "central core" of the distribution, i.e., the extent of the very central region with a respectively gentle profile, and show that the cusp formation is unlikely, even if the dark matter is cold. The obtained profile is in good agreement with observational data for at least some types of galaxies but clearly disagrees with N-body simulations.}, language = {en} } @article{GvaramadzeCheneKniazevetal.2014, author = {Gvaramadze, V. V. and Chene, A.-N. and Kniazev, A. Y. and Schnurr, O. and Shenar, Tomer and Sander, Andreas Alexander Christoph and Hainich, Rainer and Langer, N. and Hamann, Wolf-Rainer and Chu, Y.-H. and Gruendl, R. A.}, title = {Discovery of a new Wolf-Rayet star and a candidate star cluster in the Large Magellanic Cloud with Spitzer}, series = {Monthly notices of the Royal Astronomical Society}, volume = {442}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stu909}, pages = {929 -- 945}, year = {2014}, abstract = {We report the first-ever discovery of a Wolf-Rayet (WR) star in the Large Magellanic Cloud via detection of a circular shell with the Spitzer Space Telescope. Follow-up observations with Gemini-South resolved the central star of the shell into two components separated from each other by a parts per thousand 2 arcsec (or a parts per thousand 0.5 pc in projection). One of these components turns out to be a WN3 star with H and He lines both in emission and absorption (we named it BAT99 3a using the numbering system based on extending the Breysacher et al. catalogue). Spectroscopy of the second component showed that it is a B0 V star. Subsequent spectroscopic observations of BAT99 3a with the du Pont 2.5-m telescope and the Southern African Large Telescope revealed that it is a close, eccentric binary system, and that the absorption lines are associated with an O companion star. We analysed the spectrum of the binary system using the non-LTE Potsdam WR (powr) code, confirming that the WR component is a very hot (a parts per thousand 90 kK) WN star. For this star, we derived a luminosity of log L/ L-aS (TM) = 5.45 and a mass-loss rate of 10(- 5.8) M-aS (TM) yr(- 1), and found that the stellar wind composition is dominated by helium with 20 per cent of hydrogen. Spectroscopy of the shell revealed an He iii region centred on BAT99 3a and having the same angular radius (a parts per thousand 15 arcsec) as the shell. We thereby add a new example to a rare class of high-excitation nebulae photoionized by WR stars. Analysis of the nebular spectrum showed that the shell is composed of unprocessed material, implying that the shell was swept-up from the local interstellar medium. We discuss the physical relationship between the newly identified massive stars and their possible membership of a previously unrecognized star cluster.}, language = {en} } @article{KaiserNoackCordieretal.2014, author = {Kaiser, Eurika and Noack, Bernd R. and Cordier, Laurent and Spohn, Andreas and Segond, Marc and Abel, Markus and Daviller, Guillaume and Osth, Jan and Krajnovic, Sinisa and Niven, Robert K.}, title = {Cluster-based reduced-order modelling of a mixing layer}, series = {Journal of fluid mechanics}, volume = {754}, journal = {Journal of fluid mechanics}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0022-1120}, doi = {10.1017/jfm.2014.355}, pages = {365 -- 414}, year = {2014}, language = {en} } @article{ProkhorovFoersterHeetal.2014, author = {Prokhorov, Boris E. and Foerster, M. and He, M. and Namgaladze, Alexander A. and Holschneider, Matthias}, title = {Using MFACE as input in the UAM to specify the MIT dynamics}, series = {Journal of geophysical research : Space physics}, volume = {119}, journal = {Journal of geophysical research : Space physics}, number = {8}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2014JA019981}, pages = {11}, year = {2014}, abstract = {The magnetosphere-ionosphere-thermosphere (MIT) dynamic system significantly depends on the highly variable solar wind conditions, in particular, on changes of the strength and orientation of the interplanetary magnetic field (IMF). The solar wind and IMF interactions with the magnetosphere drive the MIT system via the magnetospheric field-aligned currents (FACs). The global modeling helps us to understand the physical background of this complex system. With the present study, we test the recently developed high-resolution empirical model of field-aligned currents MFACE (a high-resolution Model of Field-Aligned Currents through Empirical orthogonal functions analysis). These FAC distributions were used as input of the time-dependent, fully self-consistent global Upper Atmosphere Model (UAM) for different seasons and various solar wind and IMF conditions. The modeling results for neutral mass density and thermospheric wind are directly compared with the CHAMP satellite measurements. In addition, we perform comparisons with the global empirical models: the thermospheric wind model (HWM07) and the atmosphere density model (Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Extended 2000). The theoretical model shows a good agreement with the satellite observations and an improved behavior compared with the empirical models at high latitudes. Using the MFACE model as input parameter of the UAM model, we obtain a realistic distribution of the upper atmosphere parameters for the Northern and Southern Hemispheres during stable IMF orientation as well as during dynamic situations. This variant of the UAM can therefore be used for modeling the MIT system and space weather predictions.}, language = {en} } @article{GhoshCherstvyMetzler2014, author = {Ghosh, Surya K. and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Deformation propagation in responsive polymer network films}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {141}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {7}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4893056}, pages = {9}, year = {2014}, abstract = {We study the elastic deformations in a cross-linked polymer network film triggered by the binding of submicron particles with a sticky surface, mimicking the interactions of viral pathogens with thin films of stimulus-responsive polymeric materials such as hydrogels. From extensive Langevin Dynamics simulations we quantify how far the network deformations propagate depending on the elasticity parameters of the network and the adhesion strength of the particles. We examine the dynamics of the collective area shrinkage of the network and obtain some simple relations for the associated characteristic decay lengths. A detailed analysis elucidates how the elastic energy of the network is distributed between stretching and compression modes in response to the particle binding. We also examine the force-distance curves of the repulsion or attraction interactions for a pair of sticky particles in the polymer network film as a function of the particle-particle separation. The results of this computational study provide new insight into collective phenomena in soft polymer network films and may, in particular, be applied to applications for visual detection of pathogens such as viruses via a macroscopic response of thin films of cross-linked hydrogels. (C) 2014 AIP Publishing LLC.}, language = {en} } @article{GoychukKharchenkoMetzler2014, author = {Goychuk, Igor and Kharchenko, Vasyl O. and Metzler, Ralf}, title = {Molecular motors pulling cargos in the viscoelastic cytosol: how power strokes beat subdiffusion}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {31}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp01234h}, pages = {16524 -- 16535}, year = {2014}, abstract = {The discovery of anomalous diffusion of larger biopolymers and submicron tracers such as endogenous granules, organelles, or virus capsids in living cells, attributed to the viscoelastic nature of the cytoplasm, provokes the question whether this complex environment equally impacts the active intracellular transport of submicron cargos by molecular motors such as kinesins: does the passive anomalous diffusion of free cargo always imply its anomalously slow active transport by motors, the mean transport distance along microtubule growing sublinearly rather than linearly in time? Here we analyze this question within the widely used two-state Brownian ratchet model of kinesin motors based on the continuous-state diffusion along microtubules driven by a flashing binding potential, where the cargo particle is elastically attached to the motor. Depending on the cargo size, the loading force, the amplitude of the binding potential, the turnover frequency of the molecular motor enzyme, and the linker stiffness we demonstrate that the motor transport may turn out either normal or anomalous, as indeed measured experimentally. We show how a highly efficient normal active transport mediated by motors may emerge despite the passive anomalous diffusion of the cargo, and study the intricate effects of the elastic linker. Under different, well specified conditions the microtubule-based motor transport becomes anomalously slow and thus significantly less efficient.}, language = {en} } @article{CherstvyTeif2014, author = {Cherstvy, Andrey G. and Teif, Vladimir B.}, title = {Electrostatic effect of H1-histone protein binding on nucleosome repeat length}, series = {Physical biology : a journal for the fundamental understanding of biological systems}, volume = {11}, journal = {Physical biology : a journal for the fundamental understanding of biological systems}, number = {4}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1478-3967}, doi = {10.1088/1478-3975/11/4/044001}, pages = {6}, year = {2014}, abstract = {Within a simple biophysical model we describe the effect of electrostatic binding of H1 histone proteins on the nucleosome repeat length in chromatin. The length of wrapped DNA optimizes its binding energy to the histone core and the elastic energy penalty of DNA wrapping. The magnitude of the effect predicted from our model is in agreement with the systematic experimental data on the linear variation of nucleosome repeat lengths with H1/nucleosome ratio (Woodcock C L et al 2006 Chromos. Res. 14 17-25). We compare our model to the data for different cell types and organisms, with a widely varying ratio of bound H1 histones per nucleosome. We underline the importance of this non-specific histone-DNA charge-balance mechanism in regulating the positioning of nucleosomes and the degree of compaction of chromatin fibers in eukaryotic cells.}, language = {en} } @article{SaleemThungaKolloscheetal.2014, author = {Saleem, H. and Thunga, M. and Kollosche, Matthias and Kessler, M. R. and Laflamme, S.}, title = {Interfacial treatment effects on behavior of soft nano-composites for highly stretchable dielectrics}, series = {Polymer : the international journal for the science and technology of polymers}, volume = {55}, journal = {Polymer : the international journal for the science and technology of polymers}, number = {17}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-3861}, doi = {10.1016/j.polymer.2014.06.054}, pages = {4531 -- 4537}, year = {2014}, abstract = {We investigate the influence of interfacial treatment on the matrix filler interaction using a melt mixing process to fabricate robust and highly stretchable dielectrics. Silicone oil and silane coupling agent are studied as possible solutions to enhance the compatibility between the inorganic fillers and polymer matrix. Morphology, thermomechanical and dielectric behavior of the prepared specimens are studied. Results show that specimens filled with silicone oil coated particles have promising dielectric and thermal properties. The mechanical properties reveal a stiffness enhancement by 67\% with a high strain at break of 900\%. The relative permittivity of the specimens prepared with silicone oil increased by 45\% as observed from the dielectric analysis. (C) 2014 Elsevier Ltd. All rights reserved.}, language = {en} } @article{CherstvyPetrov2014, author = {Cherstvy, Andrey G. and Petrov, Eugene P.}, title = {Modeling DNA condensation on freestanding cationic lipid membranes}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {5}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c3cp53433b}, pages = {2020 -- 2037}, year = {2014}, abstract = {Motivated by recent experimental observations of a rapid spontaneous DNA coil-globule transition on freestanding cationic lipid bilayers, we propose simple theoretical models for DNA condensation on cationic lipid membranes. First, for a single DNA rod, we examine the conditions of full wrapping of a cylindrical DNA-like semi-flexible polyelectrolyte by an oppositely charged membrane. Then, for two parallel DNA rods, we self-consistently analyze the shape and the extent of the membrane enveloping them, focusing on membrane elastic deformations and the membrane-DNA embracing angle, which enables us to compute the membrane-mediated DNA-DNA interactions. We examine the effects of the membrane composition and its charge density, which are the experimentally tunable parameters. We show that membrane-driven rod-rod attraction is more pronounced for higher charge densities and for smaller surface tensions of the membrane. Thus, we demonstrate that for a long DNA chain adhered to a cationic lipid membrane, such membrane-induced DNA-DNA attraction can trigger compaction of DNA.}, language = {en} }