TY - GEN A1 - Oskinova, Lida T1 - Preface: X-ray emission from hot stars and their winds T2 - Advances in space research Y1 - 2016 U6 - https://doi.org/10.1016/j.asr.2016.06.031 SN - 0273-1177 SN - 1879-1948 VL - 58 SP - 679 EP - 679 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Niskanen, Johannes A1 - Kooser, Kuno A1 - Koskelo, Jaakko A1 - Käämbre, Tanel A1 - Kunnus, Kristjan A1 - Pietzsch, Annette A1 - Quevedo, Wilson A1 - Hakala, Mikko A1 - Föhlisch, Alexander A1 - Huotari, Simo A1 - Kukk, Edwin T1 - Density functional simulation of resonant inelastic X-ray scattering experiments in liquids: acetonitrile N2 - In this paper we report an experimental and computational study of liquid acetonitrile (H3C–C[triple bond, length as m-dash]N) by resonant inelastic X-ray scattering (RIXS) at the N K-edge. The experimental spectra exhibit clear signatures of the electronic structure of the valence states at the N site and incident-beam-polarization dependence is observed as well. Moreover, we find fine structure in the quasielastic line that is assigned to finite scattering duration and nuclear relaxation. We present a simple and light-to-evaluate model for the RIXS maps and analyze the experimental data using this model combined with ab initio molecular dynamics simulations. In addition to polarization-dependence and scattering-duration effects, we pinpoint the effects of different types of chemical bonding to the RIXS spectrum and conclude that the H2C–C[double bond, length as m-dash]NH isomer, suggested in the literature, does not exist in detectable quantities. We study solution effects on the scattering spectra with simulations in liquid and in vacuum. The presented model for RIXS proved to be light enough to allow phase-space-sampling and still accurate enough for identification of transition lines in physical chemistry research by RIXS. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 331 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-395133 ER - TY - GEN A1 - Nishikawa, Ken-Ichi A1 - Mizuno, Yosuke A1 - Niemiec, Jacek A1 - Kobzar, Oleh A1 - Pohl, Martin A1 - Gómez, Jose L. A1 - Duţan, Ioana A1 - Pe’er, Asaf A1 - Frederiksen, Jacob Trier A1 - Nordlund, Åke A1 - Meli, Athina A1 - Sol, Helene A1 - Hardee, Philip E. A1 - Hartmann, Dieter H. T1 - Microscopic processes in global relativistic jets containing helical magnetic fields T2 - Galaxies N2 - In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the initial evolution of both electron-proton (e(-)-p(+)) and electron-positron (e(+/-)) relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of "global" jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). In our initial simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the e(-)-p(+) jet simulation a recollimation-like instability occurs and jet electrons are strongly perturbed. In the e(+/-) jet simulation a recollimation-like instability occurs at early times followed by a kinetic instability and the general structure is similar to a simulation without helical magnetic field. Simulations using much larger systems are required in order to thoroughly follow the evolution of global jets containing helical magnetic fields. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 446 KW - relativistic jets KW - particle-in-cell simulations KW - global jets KW - helical magnetic fields KW - kinetic instabilities KW - kink instability Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407604 ER - TY - JOUR A1 - Nishikawa, Ken-Ichi A1 - Mizuno, Yosuke A1 - Niemiec, Jacek A1 - Kobzar, Oleh A1 - Pohl, Martin A1 - Gomez, Jose L. A1 - Dutan, Ioana A1 - Frederiksen, Jacob Trier A1 - Nordlund, Ake A1 - Meli, Athina A1 - Sol, Helene A1 - Hardee, Philip E. A1 - Hartmann, Dieter H. T1 - Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields JF - Galaxies : open access journal N2 - In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the initial evolution of both electron-proton (e(-)-p(+)) and electron-positron (e(+/-)) relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of "global" jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). In our initial simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the e(-)-p(+) jet simulation a recollimation-like instability occurs and jet electrons are strongly perturbed. In the e(+/-) jet simulation a recollimation-like instability occurs at early times followed by a kinetic instability and the general structure is similar to a simulation without helical magnetic field. Simulations using much larger systems are required in order to thoroughly follow the evolution of global jets containing helical magnetic fields. KW - relativistic jets KW - particle-in-cell simulations KW - global jets KW - helical magnetic fields KW - kinetic instabilities KW - kink instability Y1 - 2016 U6 - https://doi.org/10.3390/galaxies4040038 SN - 2075-4434 VL - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Nishikawa, Ken-Ichi A1 - Frederiksen, J. T. A1 - Nordlund, A. A1 - Mizuno, Y. A1 - Hardee, P. E. A1 - Niemiec, J. A1 - Gomez, J. L. A1 - Dutan, I. A1 - Meli, A. A1 - Sol, H. A1 - Pohl, Martin A1 - Hartmann, D. H. T1 - EVOLUTION OF GLOBAL RELATIVISTIC JETS: COLLIMATIONS AND EXPANSION WITH kKHI AND THE WEIBEL INSTABILITY JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - In the study of relativistic jets one of the key open questions is their interaction with the environment. Here. we study the initial evolution of both electron-proton (e(-) - p(+)) and electron-positron (e(+/-)) relativistic jets, focusing on their lateral interaction with ambient plasma. We follow the evolution of toroidal magnetic fields generated by both the kinetic Kelvin-Helmholtz and Mushroom instabilities. For an e(-) - p(+) jet, the induced magnetic field collimates the jet and electrons are perpendicularly accelerated. As the instabilities saturate and subsequently weaken, the magnetic polarity switches from clockwise to counterclockwise in the middle of the jet. For an e(+/-) jet, we find strong mixing of electrons and positrons with the ambient plasma, resulting in the creation of a bow shock. The merging of current filaments generates density inhomogeneities that. initiate a forward shock. Strong jet-ambient plasma mixing prevents a full development of the jet (on the scale studied), revealing evidence for both jet collimation and particle acceleration in the forming bow shock. Differences in the magnetic field structure generated by e(-) - p(+) and e(+/-) jets may contribute to the polarization properties of the observed emission in AGN jets and gamma-ray bursts. KW - acceleration of particles KW - plasmas KW - radiation mechanisms: non-thermal KW - relativistic processes KW - stars: jets KW - Sun: magnetic fields Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/820/2/94 SN - 0004-637X SN - 1538-4357 VL - 820 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Neher, Dieter A1 - Kniepert, Juliane A1 - Elimelech, Arik A1 - Koster, L. Jan Anton T1 - A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents JF - Scientific reports N2 - Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit a to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor. Y1 - 2016 U6 - https://doi.org/10.1038/srep24861 SN - 2045-2322 VL - 6 SP - E2348 EP - E2349 PB - Nature Publ. Group CY - London ER - TY - GEN A1 - Neher, Dieter A1 - Kniepert, Juliane A1 - Elimelech, Arik A1 - Koster, L. Jan Anton T1 - A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents N2 - Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 225 KW - Electronic and spintronic devices KW - Semiconductors Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-91414 ER - TY - JOUR A1 - Neher, Dieter A1 - Kniepert, Juliane A1 - Elimelech, Arik A1 - Koster, L. Jan Anton T1 - A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents JF - Scientific reports N2 - Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor. KW - Electronic and spintronic devices KW - Semiconductors Y1 - 2016 U6 - https://doi.org/10.1038/srep24861 SN - 2045-2322 VL - 6 PB - Nature Publishing Group CY - London ER - TY - JOUR A1 - Negrete, Jose A1 - Pumir, Alain A1 - Hsu, Hsin-Fang A1 - Westendorf, Christian A1 - Tarantola, Marco A1 - Beta, Carsten A1 - Bodenschatz, Eberhard T1 - Noisy Oscillations in the Actin Cytoskeleton of Chemotactic Amoeba JF - Physical review letters N2 - Biological systems with their complex biochemical networks are known to be intrinsically noisy. Here we investigate the dynamics of actin polymerization of amoeboid cells, which are close to the onset of oscillations. We show that the large phenotypic variability in the polymerization dynamics can be accurately captured by a generic nonlinear oscillator model in the presence of noise. We determine the relative role of the noise with a single dimensionless, experimentally accessible parameter, thus providing a quantitative description of the variability in a population of cells. Our approach, which rests on a generic description of a system close to a Hopf bifurcation and includes the effect of noise, can characterize the dynamics of a large class of noisy systems close to an oscillatory instability. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevLett.117.148102 SN - 0031-9007 SN - 1079-7114 VL - 117 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Nagornov, Roman A1 - Osipoy, Grigory A1 - Komarov, Maxim A1 - Pikovskij, Arkadij A1 - Shilnikov, Andrey T1 - Mixed-mode synchronization between two inhibitory neurons with post-inhibitory rebound JF - Communications in nonlinear science & numerical simulation N2 - We study an array of activity rhythms generated by a half-center oscillator (HCO), represented by a pair of reciprocally coupled neurons with post-inhibitory rebounds (PIR). Such coupling induced bursting possesses two time scales, one for fast spiking and another for slow quiescent periods, is shown to exhibit an array of synchronization properties. We discuss several HCO configurations constituted by two endogenous bursters, by tonic-spiking and quiescent neurons, as well as mixed-mode configurations composed of neurons of different type. We demonstrate that burst synchronization can be accompanied by complex, often chaotic, interactions of fast spikes within synchronized bursts. (C) 2015 Elsevier B.V. All rights reserved. KW - Synchronization KW - Hodgkin-Huxley model KW - Half-center oscillator KW - Post-inhibitory rebound Y1 - 2016 U6 - https://doi.org/10.1016/j.cnsns.2015.11.024 SN - 1007-5704 SN - 1878-7274 VL - 36 SP - 175 EP - 191 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Münch, Thomas A1 - Kipfstuhl, Sepp A1 - Freitag, Johannes A1 - Meyer, Hanno A1 - Laepple, Thomas T1 - Regional climate signal vs. local noise: a two-dimensional view of water isotopes in Antarctic firn at Kohnen Station, Dronning Maud Land JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - In low-accumulation regions, the reliability of delta O-18-derived temperature signals from ice cores within the Holocene is unclear, primarily due to the small climate changes relative to the intrinsic noise of the isotopic signal. In order to learn about the representativity of single ice cores and to optimise future ice-core-based climate reconstructions, we studied the stable-water isotope composition of firn at Kohnen Station, Dronning Maud Land, Antarctica. Analysing delta O-18 in two 50m long snow trenches allowed us to create an unprecedented, two-dimensional image characterising the isotopic variations from the centimetre to the 100-metre scale. Our results show seasonal layering of the isotopic composition but also high horizontal isotopic variability caused by local stratigraphic noise. Based on the horizontal and vertical structure of the isotopic variations, we derive a statistical noise model which successfully explains the trench data. The model further allows one to determine an upper bound for the reliability of climate reconstructions conducted in our study region at seasonal to annual resolution, depending on the number and the spacing of the cores taken. Y1 - 2016 U6 - https://doi.org/10.5194/cp-12-1565-2016 SN - 1814-9324 SN - 1814-9332 VL - 12 SP - 1565 EP - 1581 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Mueller, Lars A1 - Nanova, Diana A1 - Glaser, Tobias A1 - Beck, Sebastian A1 - Pucci, Annemarie A1 - Kast, Anne K. A1 - Schroeder, Rasmus R. A1 - Mankel, Eric A1 - Pingel, Patrick A1 - Neher, Dieter A1 - Kowalsky, Wolfgang A1 - Lovrincic, Robert T1 - Charge-Transfer-Solvent Interaction Predefines Doping Efficiency in p-Doped P3HT Films JF - Chemistry of materials : a publication of the American Chemical Society N2 - Efficient electrical doping of organic semiconductors is a necessary prerequisite for the fabrication of high performance organic electronic devices. In this work, we study p-type doping of poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) spin-cast from two different solvents. Using electron diffraction, we find strong dopant-induced pi-pi-stacking for films from the solvent chloroform, but not from chlorobenzene. This image is confirmed and expanded by the analysis of vibrational features of P3HT and polaron absorptions using optical spectroscopy. Here, a red-shifted polaron absorption is found in doped films from chloroform, caused by a higher conjugation length of the polymer backbone. These differences result in a higher conductivity of films from chloroform. We use optical spectroscopy on the corresponding blend solutions to shed light on the origin of this effect and propose a model to explain why solutions of doped P3HT reveal more aggregation of charged molecules in chlorobenzene, whereas more order is finally observed in dried films from chloroform. Our study emphasizes the importance of solvent parameters exceeding the bare solubility of pure dopant and host material for the preparation of highly conductive doped films. Y1 - 2016 U6 - https://doi.org/10.1021/acs.chemmater.6b01629 SN - 0897-4756 SN - 1520-5002 VL - 28 SP - 4432 EP - 4439 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Moretti, M. I. A1 - Clementini, Gisella A1 - Marconi, V. Ripepi M. A1 - Rubele, S. A1 - Cioni, Maria-Rosa L. A1 - Muraveva, T. A1 - Groenewegen, M. A. T. A1 - Cross, N. J. G. A1 - Ivanov, V. D. A1 - Piatti, A. E. A1 - de Grijs, Richard T1 - The VMC survey - XX. Identification of new Cepheids in the Small Magellanic Cloud JF - Monthly notices of the Royal Astronomical Society N2 - We present K-s-band light curves for 299 Cepheids in the Small Magellanic Cloud (SMC) of which 288 are new discoveries that we have identified using multi-epoch near-infrared photometry obtained by the VISTA survey of the Magellanic Clouds system (VMC). The new Cepheids have periods in the range from 0.34 to 9.1 d and cover the magnitude interval 12.9 <= currency sign < K-s > <= currency sign 17.6 mag. Our method was developed using variable stars previously identified by the optical microlensing survey OGLE. We focus on searching new Cepheids in external regions of the SMC for which complete VMC K-s-band observations are available and no comprehensive identification of different types of variable stars from other surveys exists yet. KW - methods: data analysis KW - surveys KW - stars: variables: Cepheids KW - Magellanic Clouds Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stw716 SN - 0035-8711 SN - 1365-2966 VL - 459 SP - 1687 EP - 1697 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Moradi, N. A1 - Zakrevskyy, Yuriy A1 - Javadi, A. A1 - Aksenenko, E. V. A1 - Fainerman, V. B. A1 - Lomadze, Nino A1 - Santer, Svetlana A1 - Miller, R. T1 - Surface tension and dilation rheology of DNA solutions in mixtures with azobenzene-containing cationic surfactant JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - The surface tension and dilational surface visco-elasticity of the individual solutions of the biopolymer DNA and the azobenzene-containing cationic surfactant AzoTAB, as well as their mixtures were measured using the drop profile analysis tensiometry. The negatively charged DNA molecules form complexes with the cationic surfactant AzoTAB. Mixed DNA + AzoTAB solutions exhibit high surface activity and surface layer elasticity. Extremes in the dependence of these characteristics on the AzoTAB concentration exist within the concentration range of 3 x 10(-6)-5 x 10(-5) M. The surface tension of the mixture shows a minimum with a subsequent maximum. In the same concentration range the elasticity shows first a maximum and then a subsequent minimum. A recently developed thermodynamic model was modified to account for the dependence of the adsorption equilibrium constant of the adsorbed complex on the cationic surfactant concentration. This modified theory shows good agreement with the experimental data both for the surface tension and the elasticity values over the entire range of studied AzoTAB concentrations. (C) 2016 Elsevier B.V. All rights reserved. KW - Mixed adsorption layers KW - Polymer/surfactant interaction KW - Water/air interface KW - Thermodynamics of adsorption KW - Dilational rheology KW - Drop profile analysis tensiometry Y1 - 2016 U6 - https://doi.org/10.1016/j.colsurfa.2016.04.021 SN - 0927-7757 SN - 1873-4359 VL - 505 SP - 186 EP - 192 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Metzler, Ralf A1 - Jeon, J. -H. A1 - Cherstvy, Andrey G. T1 - Non-Brownian diffusion in lipid membranes: Experiments and simulations JF - Biochimica et biophysica acta : Biomembranes N2 - The dynamics of constituents and the surface response of cellular membranes also in connection to the binding of various particles and macromolecules to the membrane are still a matter of controversy in the membrane biophysics community, particularly with respect to crowded membranes of living biological cells. We here put into perspective recent single particle tracking experiments in the plasma membranes of living cells and supercomputing studies of lipid bilayer model membranes with and without protein crowding. Special emphasis is put on the observation of anomalous, non-Brownian diffusion of both lipid molecules and proteins embedded in the lipid bilayer. While single component, pure lipid bilayers in simulations exhibit only transient anomalous diffusion of lipid molecules on nanosecond time scales, the persistence of anomalous diffusion becomes significantly longer ranged on the addition of disorder through the addition of cholesterol or proteins and on passing of the membrane lipids to the gel phase. Concurrently, experiments demonstrate the anomalous diffusion of membrane embedded proteins up to macroscopic time scales in the minute time range. Particular emphasis will be put on the physical character of the anomalous diffusion, in particular, the occurrence of ageing observed in the experiments the effective diffusivity of the measured particles is a decreasing function of time. Moreover, we present results for the time dependent local scaling exponent of the mean squared displacement of the monitored particles. Recent results finding deviations from the commonly assumed Gaussian diffusion patterns in protein crowded membranes are reported. The properties of the displacement autocorrelation function of the lipid molecules are discussed in the light of their appropriate physical anomalous diffusion models, both for non-crowded and crowded membranes. In the last part of this review we address the upcoming field of membrane distortion by elongated membrane-binding particles. We discuss how membrane compartmentalisation and the particle-membrane binding energy may impact the dynamics and response of lipid membranes. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Rog. (C) 2016 The Authors. Published by Elsevier B.V. KW - Lipid bilayer KW - Protein crowding KW - Anomalous diffusion KW - Simulations KW - Stochastic modelling KW - Non-Gaussian Y1 - 2016 U6 - https://doi.org/10.1016/j.bbamem.2016.01.022 SN - 0005-2736 SN - 0006-3002 VL - 1858 SP - 2451 EP - 2467 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Metzler, Ralf T1 - PROTEIN PHYSICS Forever ageing T2 - Nature physics N2 - Single-molecule techniques have long given us insight into the motion and interactions of individual molecules. But simulations now show that the dynamics inside single proteins is not as simple as we thought — and that proteins are forever changing. Y1 - 2016 U6 - https://doi.org/10.1038/nphys3585 SN - 1745-2473 SN - 1745-2481 VL - 12 SP - 113 EP - 114 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Mengel, Matthias A1 - Feldmann, Johannes A1 - Levermann, Anders T1 - Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin JF - Nature climate change N2 - Antarctica’s contribution to global sea-level rise has recently been increasing1. Whether its ice discharge will become unstable and decouple from anthropogenic forcing2,3,4 or increase linearly with the warming of the surrounding ocean is of fundamental importance5. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica’s Filchner–Ronne ice shelf within the next two centuries6,7. The ice basin’s retrograde bed slope would allow for an unstable ice-sheet retreat8, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability9,10,11. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner–Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming12, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability. Y1 - 2016 U6 - https://doi.org/10.1038/NCLIMATE2808 SN - 1758-678X SN - 1758-6798 VL - 6 SP - 71 EP - + PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Mazurek, P. A1 - Yu, L. A1 - Gerhard, Reimund A1 - Wirges, Werner A1 - Skov, A. L. T1 - Glycerol as high-permittivity liquid filler in dielectric silicone elastomers JF - Journal of applied polymer science N2 - A recently reported novel class of elastomers was tested with respect to its dielectric properties. The new elastomer material is based on a commercially available poly(dimethylsiloxane) composition, which has been modified by embedding glycerol droplets into its matrix. The approach has two major advantages that make the material useful in a dielectric actuator. First, the glycerol droplets efficiently enhance the dielectric constant, which can reach astonishingly high values in the composite. Second, the liquid filler also acts as a softener that effectively decreases the elastic modulus of the composite. In combination with very low cost and easy preparation, the two property enhancements lead to an extremely attractive dielectric elastomer material. Experimental permittivity data are compared to various theoretical models that predict relative permittivity changes as a function of filler loading, and the applicability of the models is discussed. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44153. KW - crosslinking KW - dielectric properties KW - elastomers KW - sensors and actuators Y1 - 2016 U6 - https://doi.org/10.1002/app.44153 SN - 0021-8995 SN - 1097-4628 VL - 133 PB - Wiley-Blackwell CY - Hoboken ER - TY - THES A1 - Marx, Robert T1 - A quantitative model of spatial correlations in parametric down conversion for investigating complementarity at a double slit Y1 - 2016 ER - TY - JOUR A1 - Martinez Gonzalez, M. J. A1 - Pastor Yabar, A. A1 - Lagg, A. A1 - Asensio Ramos, A. A1 - Collados Vera, M. A1 - Solanki, S. K. A1 - Balthasar, H. A1 - Berkefeld, T. A1 - Denker, Carsten A1 - Doerr, H. P. A1 - Feller, A. A1 - Franz, M. A1 - González Manrique, Sergio Javier A1 - Hofmann, A. A1 - Kneer, F. A1 - Kuckein, Christoph A1 - Louis, R. A1 - von der Lühe, O. A1 - Nicklas, H. A1 - Orozco, D. A1 - Rezaei, R. A1 - Schlichenmaier, R. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Sigwarth, M. A1 - Sobotka, M. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Verma, Meetu A1 - Waldman, T. A1 - Volkmer, R. T1 - Inference of magnetic fields in the very quiet Sun JF - Journal of geophysical research : Earth surface N2 - Context. Over the past 20 yr, the quietest areas of the solar surface have revealed a weak but extremely dynamic magnetism occurring at small scales (<500 km), which may provide an important contribution to the dynamics and energetics of the outer layers of the atmosphere. Understanding this magnetism requires the inference of physical quantities from high-sensitivity spectro-polarimetric data with high spatio-temporal resolution. Aims. We present high-precision spectro-polarimetric data with high spatial resolution (0.4") of the very quiet Sun at 1.56 mu m obtained with the GREGOR telescope to shed some light on this complex magnetism. Methods. We used inversion techniques in two main approaches. First, we assumed that the observed profiles can be reproduced with a constant magnetic field atmosphere embedded in a field-free medium. Second, we assumed that the resolution element has a substructure with either two constant magnetic atmospheres or a single magnetic atmosphere with gradients of the physical quantities along the optical depth, both coexisting with a global stray-light component. Results. Half of our observed quiet-Sun region is better explained by magnetic substructure within the resolution element. However, we cannot distinguish whether this substructure comes from gradients of the physical parameters along the line of sight or from horizontal gradients (across the surface). In these pixels, a model with two magnetic components is preferred, and we find two distinct magnetic field populations. The population with the larger filling factor has very weak (similar to 150 G) horizontal fields similar to those obtained in previous works. We demonstrate that the field vector of this population is not constrained by the observations, given the spatial resolution and polarimetric accuracy of our data. The topology of the other component with the smaller filling factor is constrained by the observations for field strengths above 250 G: we infer hG fields with inclinations and azimuth values compatible with an isotropic distribution. The filling factors are typically below 30%. We also find that the flux of the two polarities is not balanced. From the other half of the observed quiet-Sun area similar to 50% are two-lobed Stokes V profiles, meaning that 23% of the field of view can be adequately explained with a single constant magnetic field embedded in a non-magnetic atmosphere. The magnetic field vector and filling factor are reliable inferred in only 50% based on the regular profiles. Therefore, 12% of the field of view harbour hG fields with filling factors typically below 30%. At our present spatial resolution, 70% of the pixels apparently are non-magnetised. KW - Sun: atmosphere KW - Sun: magnetic fields KW - techniques: polarimetric KW - methods: observational Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201628449 SN - 1432-0746 VL - 596 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Martin, Nicolas F. A1 - Jungbluth, Valentin A1 - Nidever, David L. A1 - Bell, Eric F. A1 - Besla, Gurtina A1 - Blum, Robert D. A1 - Cioni, Maria-Rosa L. A1 - Conn, Blair C. A1 - Kaleida, Catherine C. A1 - Gallart, Carme A1 - Jin, Shoko A1 - Majewski, Steven R. A1 - Martinez-Delgado, David A1 - Monachesi, Antonela A1 - Munoz, Ricardo R. A1 - Noel, Noelia E. D. A1 - Olsen, Knut A1 - Stringfellow, Guy S. A1 - van der Marel, Roeland P. A1 - Vivas, A. Katherina A1 - Walker, Alistair R. A1 - Zaritsky, Dennis T1 - SMASH 1: A VERY FAINT GLOBULAR CLUSTER DISRUPTING IN THE OUTER REACHES OF THE LMC? JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters KW - globular clusters: individual: (SMASH 1) KW - Local Group KW - Magellanic Clouds Y1 - 2016 U6 - https://doi.org/10.3847/2041-8205/830/1/L10 SN - 2041-8205 SN - 2041-8213 VL - 830 SP - 92 EP - 98 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Lu, Guanghao A1 - Di Pietro, Riccardo A1 - Kölln, Lisa Sophie A1 - Nasrallah, Iyad A1 - Zhou, Ling A1 - Mollinger, Sonya A1 - Himmelberger, Scott A1 - Koch, Norbert A1 - Salleo, Alberto A1 - Neher, Dieter T1 - Dual-Characteristic Transistors Based on Semiconducting Polymer Blends JF - Advanced electronic materials N2 - A dual-characteristic polymer field-effect transistor has markedly different characteristics in low and high voltage operations. In the low-voltage range (<5 V) it shows sharp subthreshold slopes (0.3–0.4 V dec−1), using which a low-voltage inverter with gain 8 is realized, while high-voltage (>5 V) induces symmetric current with regard to drain and gate voltages, leading to discrete differential (trans) conductances. KW - charge accumulation KW - crystalline ordering KW - field-effect-transistor KW - semiconducting polymers Y1 - 2016 U6 - https://doi.org/10.1002/aelm.201600267 SN - 2199-160X VL - 2 SP - 2344 EP - 2351 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Love, John A. A1 - Chou, Shu-Hua A1 - Huang, Ye A1 - Bazan, Guillermo C. A1 - Thuc-Quyen Nguyen, T1 - Effects of solvent additive on "s-shaped" curves in solution-processed small molecule solar cells JF - Beilstein journal of organic chemistry N2 - A novel molecular chromophore, p-SIDT(FBTThCA8)(2), is introduced as an electron-donor material for bulk heterojunction (BHJ) solar cells with broad absorption and near ideal energy levels for the use in combination with common acceptor materials. It is found that films cast from chlorobenzene yield devices with strongly s-shaped current-voltage curves, drastically limiting performance. We find that addition of the common solvent additive diiodooctane, in addition to facilitating crystallization, leads to improved vertical phase separation. This yields much better performing devices, with improved curve shape, demonstrating the importance of morphology control in BHJ devices and improving the understanding of the role of solvent additives. KW - current voltage analysis KW - morphology KW - organic solar cells Y1 - 2016 U6 - https://doi.org/10.3762/bjoc.12.249 SN - 1860-5397 VL - 12 SP - 2543 EP - 2555 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, Main ER - TY - JOUR A1 - Loebner, Sarah A1 - Jelken, Joachim A1 - Yadavalli, Nataraja Sekhar A1 - Sava, Elena A1 - Hurduc, Nicolae A1 - Santer, Svetlana T1 - Motion of Adsorbed Nano-Particles on Azobenzene Containing Polymer Films JF - Molecules N2 - We demonstrate in situ recorded motion of nano-objects adsorbed on a photosensitive polymer film. The motion is induced by a mass transport of the underlying photoresponsive polymer material occurring during irradiation with interference pattern. The polymer film contains azobenzene molecules that undergo reversible photoisomerization reaction from trans-to cis-conformation. Through a multi-scale chain of physico-chemical processes, this finally results in the macro-deformations of the film due to the changing elastic properties of polymer. The topographical deformation of the polymer surface is sensitive to a local distribution of the electrical field vector that allows for the generation of dynamic changes in the surface topography during irradiation with different light interference patterns. Polymer film deformation together with the motion of the adsorbed nano-particles are recorded using a homemade set-up combining an optical part for the generation of interference patterns and an atomic force microscope for acquiring the surface deformation. The particles undergo either translational or rotational motion. The direction of particle motion is towards the topography minima and opposite to the mass transport within the polymer film. The ability to relocate particles by photo-induced dynamic topography fluctuation offers a way for a non-contact simultaneous manipulation of a large number of adsorbed particles just in air at ambient conditions. KW - motion of adsorbed nano-particles KW - azobenzene containing polymer films KW - fluctuating surfaces Y1 - 2016 U6 - https://doi.org/10.3390/molecules21121663 SN - 1420-3049 VL - 21 SP - 397 EP - 411 PB - MDPI CY - Basel ER - TY - JOUR A1 - Liu, Xiaodong A1 - Sachse, Manuel A1 - Spahn, Frank A1 - Schmidt, Jurgen T1 - Dynamics and distribution of Jovian dust ejected from the Galilean satellites JF - Journal of geophysical research, Planets N2 - In this paper, the dynamical analysis of the Jovian dust originating from the four Galilean moons is presented. High-accuracy orbital integrations of dust particles are used to determine their dynamical evolution. A variety of forces are taken into account, including the Lorentz force, solar radiation pressure, Poynting-Robertson drag, solar gravity, the satellites' gravity, plasma drag, and gravitational effects due to nonsphericity of Jupiter. More than 20,000 dust particles from each source moon in the size range from 0.05 μm to 1 cm are simulated over 8000 (Earth) years until each dust grain hits a sink (moons, Jupiter, or escape from the system). Configurations of dust number density in the Jovicentric equatorial inertial frame are calculated and shown. In a Jovicentric frame rotating with the Sun the dust distributions are found to be asymmetric. For certain small particle sizes, the dust population is displaced towards the Sun, while for certain larger sizes, the dust population is displaced away from the Sun. The average lifetime as a function of particle size for ejecta from each source moon is derived, and two sharp jumps in the average lifetime are analyzed. Transport of dust between the Galilean moons and to Jupiter is investigated. Most of the orbits for dust particles from Galilean moons are prograde, while, surprisingly, a small fraction of orbits are found to become retrograde mainly due to solar radiation pressure and Lorentz force. The distribution of orbital elements is also analyzed. Y1 - 2016 U6 - https://doi.org/10.1002/2016JE004999 SN - 2169-9097 SN - 2169-9100 VL - 121 SP - 1141 EP - 1173 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Liu, Rui A1 - Kliem, Bernhard A1 - Titov, Viacheslav S. A1 - Chen, Jun A1 - Wang, Yuming A1 - Wang, Haimin A1 - Liu, Chang A1 - Xu, Yan A1 - Wiegelmann, Thomas T1 - STRUCTURE, STABILITY, AND EVOLUTION OF MAGNETIC FLUX ROPES FROM THE PERSPECTIVE OF MAGNETIC TWIST JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We investigate the evolution of NOAA Active Region (AR) 11817 during 2013 August 10–12, when it developed a complex field configuration and produced four confined, followed by two eruptive, flares. These C-and-above flares are all associated with a magnetic flux rope (MFR) located along the major polarity inversion line, where shearing and converging photospheric flows are present. Aided by the nonlinear force-free field modeling, we identify the MFR through mapping magnetic connectivities and computing the twist number ${{ \mathcal T }}_{w}$ for each individual field line. The MFR is moderately twisted ($| {{ \mathcal T }}_{w}| \lt 2$) and has a well-defined boundary of high squashing factor Q. We found that the field line with the extremum $| {{ \mathcal T }}_{w}| $ is a reliable proxy of the rope axis, and that the MFR's peak $| {{ \mathcal T }}_{w}| $ temporarily increases within half an hour before each flare while it decreases after the flare peak for both confined and eruptive flares. This pre-flare increase in $| {{ \mathcal T }}_{w}| $ has little effect on the AR's free magnetic energy or any other parameters derived for the whole region, due to its moderate amount and the MFR's relatively small volume, while its decrease after flares is clearly associated with the stepwise decrease in the whole region's free magnetic energy due to the flare. We suggest that ${{ \mathcal T }}_{w}$ may serve as a useful parameter in forewarning the onset of eruption, and therefore, the consequent space weather effects. The helical kink instability is identified as the prime candidate onset mechanism for the considered flares. KW - coronal mass ejections (CMEs) KW - Sun: corona KW - Sun: filaments, pominences KW - Sun: flares KW - Sun: magnetic fields Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/818/2/148 SN - 0004-637X SN - 1538-4357 VL - 818 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Ligorio, G. A1 - Nardi, M. V. A1 - Steyrleuthner, Robert A1 - Ihiawakrim, D. A1 - Crespo-Monteiro, N. A1 - Brinkmann, Martin A1 - Neher, Dieter A1 - Koch, N. T1 - Metal nanoparticle mediated space charge and its optical control in an organic hole-only device JF - Applied physics letters N2 - We reveal the role of localized space charges in hole-only devices based on an organic semiconductor with embedded metal nanoparticles (MNPs). MNPs act as deep traps for holes and reduce the current density compared to a device without MNPs by a factor of 10(4) due to the build-up of localized space charge. Dynamic MNPs charged neutrality can be realized during operation by electron transfer from excitons created in the organic matrix, enabling light sensing independent of device bias. In contrast to the previous speculations, electrical bistability in such devices was not observed. (C) 2016 AIP Publishing LLC. Y1 - 2016 U6 - https://doi.org/10.1063/1.4945710 SN - 0003-6951 SN - 1077-3118 VL - 108 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Reinecke, Antje A1 - Koetz, Joachim T1 - "Green" gold nanotriangles: synthesis, purification by polyelectrolyte/micelle depletion flocculation and performance in surface-enhanced Raman scattering JF - RSC Advances N2 - The aim of this study was to develop a one-step synthesis of gold nanotriangles (NTs) in the presence of mixed phospholipid vesicles followed by a separation process to isolate purified NTs. Negatively charged vesicles containing AOT and phospholipids, in the absence and presence of additional reducing agents (polyampholytes, polyanions or low molecular weight compounds), were used as a template phase to form anisotropic gold nanoparticles. Upon addition of the gold chloride solution, the nucleation process is initiated and both types of particles, i.e., isotropic spherical and anisotropic gold nanotriangles, are formed simultaneously. As it was not possible to produce monodisperse nanotriangles with such a one-step procedure, the anisotropic nanoparticles needed to be separated from the spherical ones. Therefore, a new type of separation procedure using combined polyelectrolyte/micelle depletion flocculation was successfully applied. As a result of the different purification steps, a green colored aqueous dispersion was obtained containing highly purified, well-defined negatively charged flat nanocrystals with a platelet thickness of 10 nm and an edge length of about 175 nm. The NTs produce promising results in surface-enhanced Raman scattering. Y1 - 2016 U6 - https://doi.org/10.1039/c6ra04808k SN - 2046-2069 VL - 6 SP - 33561 EP - 33568 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Levermann, Anders A1 - Winkelmann, Ricarda T1 - A simple equation for the melt elevation feedback of ice sheets JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - In recent decades, the Greenland Ice Sheet has been losing mass and has thereby contributed to global sea-level rise. The rate of ice loss is highly relevant for coastal protection worldwide. The ice loss is likely to increase under future warming. Beyond a critical temperature threshold, a meltdown of the Greenland Ice Sheet is induced by the self-enforcing feedback between its lowering surface elevation and its increasing surface mass loss: the more ice that is lost, the lower the ice surface and the warmer the surface air temperature, which fosters further melting and ice loss. The computation of this rate so far relies on complex numerical models which are the appropriate tools for capturing the complexity of the problem. By contrast we aim here at gaining a conceptual understanding by deriving a purposefully simple equation for the self-enforcing feedback which is then used to estimate the melt time for different levels of warming using three observable characteristics of the ice sheet itself and its surroundings. The analysis is purely conceptual in nature. It is missing important processes like ice dynamics for it to be useful for applications to sea-level rise on centennial timescales, but if the volume loss is dominated by the feedback, the resulting logarithmic equation unifies existing numerical simulations and shows that the melt time depends strongly on the level of warming with a critical slow-down near the threshold: the median time to lose 10% of the present-day ice volume varies between about 3500 years for a temperature level of 0.5 degrees C above the threshold and 500 years for 5 degrees C. Unless future observations show a significantly higher melting sensitivity than currently observed, a complete meltdown is unlikely within the next 2000 years without significant ice-dynamical contributions. Y1 - 2016 U6 - https://doi.org/10.5194/tc-10-1799-2016 SN - 1994-0416 SN - 1994-0424 VL - 10 SP - 1799 EP - 1807 PB - Copernicus CY - Göttingen ER - TY - GEN A1 - Levermann, Anders A1 - Petoukhov, Vladimir A1 - Schewe, Jacob A1 - Schellnhuber, Hans Joachim T1 - Abrupt monsoon transitions as seen in paleorecords can be explained by moisture-advection feedback T2 - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2016 U6 - https://doi.org/10.1073/pnas.1603130113 SN - 0027-8424 VL - 113 SP - E2348 EP - E2349 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Leonhardt, Helmar A1 - Gerhardt, Matthias A1 - Hoeppner, Nadine A1 - Krüger, Kirsten A1 - Tarantola, Marco A1 - Beta, Carsten T1 - Cell-substrate impedance fluctuations of single amoeboid cells encode cell-shape and adhesion dynamics JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We show systematic electrical impedance measurements of single motile cells on microelectrodes. Wild-type cells and mutant strains were studied that differ in their cell-substrate adhesion strength. We recorded the projected cell area by time-lapse microscopy and observed irregular oscillations of the cell shape. These oscillations were correlated with long-term variations in the impedance signal. Superposed to these long-term trends, we observed fluctuations in the impedance signal. Their magnitude clearly correlated with the adhesion strength, suggesting that strongly adherent cells display more dynamic cell-substrate interactions. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevE.93.012414 SN - 2470-0045 SN - 2470-0053 VL - 93 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Lenske, Gerlinde A1 - Wagner, Wolfgang A1 - Wirth, Joachim A1 - Thillmann, Hubertina A1 - Cauet, Eva A1 - Liepertz, Sven A1 - Leutner, Detlev T1 - The importance of pedagogical knowledge for classroom management and for and for students’ achievement JF - Zeitschrift für Erziehungswissenschaft N2 - Im Rahmen der vorliegenden Studie wurde untersucht, ob das pädagogisch-psychologische Wissen von Lehrkräften die prozessuale Qualität des Physikunterrichts mit Blick auf die Klassenführung und den Lernzuwachs der Schülerinnen und Schüler beeinflusst. Das pädagogisch-psychologische Professionswissen, konzeptualisiert als ein fächerübergreifendes, handlungsleitendes Wissen über Strategien und Mittel zur Unterrichtsgestaltung, wurde über einen Paper-Pencil-Test, bestehend aus einer Skala zum deklarativen und einer Skala zum konditional-prozeduralen Wissen erhoben (Lenske et al. 2015). Als ein grundlegendes Merkmal prozessualer Unterrichtsqualität wurde die Klassenführung anhand von Videoratings zu zwei Messzeitpunkten (zwei Unterrichtsstunden) erfasst. Der Lernzuwachs der Schülerinnen und Schüler wurde über standardisierte Fachwissenstests im Prä-Post-Testdesign gemessen. Die Stichprobe umfasst 34 Gymnasiallehrkräfte und deren Schülerinnen und Schüler (N = 993). Auf Basis eines Complex-Bootstrap-Mediations-Modells zeigte sich, dass das pädagogisch-psychologische Professionswissen über die Klassenführung vermittelt den Lernzuwachs der Schüler und Schülerinnen positiv beeinflusst. In the present study it was investigated whether the pedagogical knowledge of teachers has an influence on the process quality of physics instruction and on the learning achievement of students as well. Pedagogical knowledge, conceptualized as knowledge about strategies in classroom instruction that is domain-general and relevant for teaching behaviors, was measured using a paper-and-pencil test with two scales: one scale on declarative knowledge, the other on conditional-procedural knowledge (Lenske et al. 2015). As a basic aspect of the process quality of classroom instruction, classroom management was assessed using video ratings of two lessons from each participating teacher. Students’ learning achievement was assessed using standardized domain-specific knowledge tests in a pretest-posttest design. The sample included 34 teachers from higher-track secondary schools and their students (N = 993). A complex bootstrapping mediation model shows that teachers’ pedagogical knowledge, mediated by their classroom management, has a positive effect on their students’ learning achievement. KW - Classroom management KW - Instructional quality KW - Mediation-model KW - Pedagogical professional knowledge KW - Professional knowledge Y1 - 2016 U6 - https://doi.org/10.1007/s11618-015-0659-x SN - 1434-663X SN - 1862-5215 VL - 19 SP - 211 EP - 233 PB - Springer CY - Wiesbaden ER - TY - THES A1 - Lehmann, Jascha In-su T1 - Changes in extratropical storm track activity and their implications for extreme weather events Y1 - 2016 ER - TY - JOUR A1 - Lechleitner, Franziska A. A1 - Baldini, James U. L. A1 - Breitenbach, Sebastian Franz Martin A1 - Fohlmeister, Jens Bernd A1 - McIntyre, Cameron A1 - Goswami, Bedartha A1 - Jamieson, Robert A. A1 - van der Voort, Tessa S. A1 - Prufer, Keith A1 - Marwan, Norbert A1 - Culleton, Brendan J. A1 - Kennett, Douglas J. A1 - Asmerom, Yemane A1 - Polyak, Victor A1 - Eglinton, Timothy I. T1 - Hydrological and climatological controls on radiocarbon concentrations in a tropical stalagmite JF - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society N2 - Precisely-dated stalagmites are increasingly important archives for the reconstruction of terrestrial paleoclimate at very high temporal resolution. In-depth understanding of local conditions at the cave site and of the processes driving stalagmite deposition is of paramount importance for interpreting proxy signals incorporated in stalagmite carbonate. Here we present a sub-decadally resolved dead carbon fraction (DCF) record for a stalagmite from Yok Balum Cave (southern Belize). The record is coupled to parallel stable carbon isotope (delta C-13) and U/Ca measurements, as well as radiocarbon (C-14) measurements from soils overlying the cave system. Using a karst carbon cycle model we disentangle the importance of soil and karst processes on stalagmite DCF incorporation, revealing a dominant host rock dissolution control on total DCF. Covariation between DCF, delta C-13, and U/Ca indicates that karst processes are a common driver of all three parameters, suggesting possible use of delta C-13 and trace element ratios to independently quantify DCF variability. A statistically significant multi-decadal lag of variable length exists between DCF and reconstructed solar activity, suggesting that solar activity influenced regional precipitation in Mesoamerica over the past 1500 years, but that the relationship was non-static. Although the precise nature of the observed lag is unclear, solar-induced changes in North Atlantic oceanic and atmospheric dynamics may play a role. (C) 2016 Elsevier Ltd. All rights reserved. KW - Stalagmite KW - Tropics KW - Radiocarbon KW - Trace elements KW - Hydroclimate Y1 - 2016 U6 - https://doi.org/10.1016/j.gca.2016.08.039 SN - 0016-7037 SN - 1872-9533 VL - 194 SP - 233 EP - 252 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Laepple, Thomas A1 - Hörhold, Maria A1 - Münch, Thomas A1 - Freitag, Johannes A1 - Wegner, Anna A1 - Kipfstuhl, Sepp T1 - Layering of surface snow and firn at Kohnen Station, Antarctica: Noise or seasonal signal? JF - Journal of geophysical research : Earth surface N2 - The density of firn is an important property for monitoring and modeling the ice sheets as well as to model the pore close-off and thus to interpret ice core-based greenhouse gas records. One feature, which is still in debate, is the potential existence of an annual cycle of firn density in low-accumulation regions. Several studies describe or assume seasonally successive density layers, horizontally evenly distributed, as seen in radar data. On the other hand, high-resolution density measurements on firn cores in Antarctica and Greenland show no clear seasonal cycle in the top few meters. A major caveat of most existing snow-pit and firn-core-based studies is that they represent one vertical profile from a laterally heterogeneous density field. To overcome this, we created an extensive data set of horizontal and vertical density data at Kohnen Station, Dronning Maud Land, on the East Antarctic Plateau. We drilled and analyzed three 90m long firn cores as well as 143 one-meter-long vertical profiles from two elongated snow trenches to obtain a two-dimensional view of the density variations. The analysis of the 45m wide and 1m deep density fields reveals a seasonal cycle in density. However, the seasonality is overprinted by strong stratigraphic noise, making it invisible when analyzing single firn cores. Our density data set extends the view from the local ice core perspective to a hundred meter scale and thus supports linking spatially integrating methods such as radar and seismic studies to ice and firn cores. Y1 - 2016 U6 - https://doi.org/10.1002/2016JF003919 SN - 2169-9003 SN - 2169-9011 VL - 121 SP - 1849 EP - 1860 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Kuznetsov, Sergey P. T1 - Parametric chaos generator operating on a varactor diode with the instability limitation decay mechanism JF - Technical Physics N2 - Equations are derived for a parametric chaos generator containing three oscillatory circuits and a variable-capacitance diode (varactor) and are reduced to equations for slow amplitudes of parametrically interacting modes. With allowance for quadratic nonlinearity, the problem is reduced to a system of three first-order differential equations for Pikovsky-Rabinovich-Trakhtengerts real amplitudes with a Lorenz-type attractor. In a more accurate description of nonlinearity of the varactor, the equations for slow amplitudes are complex-valued, which leads to the loss of robustness of chaotic dynamics, which is typical of the Lorenz attractor. The results of numerical calculations (portraits of attractors and Lyapunov exponents) in models with different approximation levels are compared. Y1 - 2016 U6 - https://doi.org/10.1134/S1063784216030129 SN - 1063-7842 SN - 1090-6525 VL - 61 SP - 436 EP - 445 PB - Pleiades Publ. CY - New York ER - TY - JOUR A1 - Kuznetsov, Alexander P. A1 - Turukina, Ludmila V. A1 - Chernyshov, Nikolai Yu A1 - Sedova, Yuliya V. T1 - Oscillations and Synchronization in a System of Three Reactively Coupled Oscillators JF - International journal of bifurcation and chaos : in applied sciences and engineering N2 - We consider a system of three interacting van der Pol oscillators with reactive coupling. Phase equations are derived, using proper order of expansion over the coupling parameter. The dynamics of the system is studied by means of the bifurcation analysis and with the method of Lyapunov exponent charts. Essential and physically meaningful features of the reactive coupling are discussed. KW - Synchronization KW - quasi-periodic oscillation KW - bifurcation KW - chaos Y1 - 2016 U6 - https://doi.org/10.1142/S0218127416500103 SN - 0218-1274 SN - 1793-6551 VL - 26 SP - 31 EP - 39 PB - World Scientific CY - Singapore ER - TY - GEN A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend N2 - Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 228 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-91541 ER - TY - JOUR A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend JF - Scientific reports N2 - Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. Y1 - 2016 U6 - https://doi.org/10.1038/srep26832 SN - 2045-2322 VL - 6 PB - Nature Publishing Group CY - London ER - TY - JOUR A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Dispersive Non-Geminate Recombination in an Amorphous Polymer: Fullerene Blend JF - Scientific reports N2 - Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer: fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. Y1 - 2016 U6 - https://doi.org/10.1038/srep26832 SN - 2045-2322 VL - 6 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Zhang, Wenkai A1 - Delcey, Mickael G. A1 - Pinjari, Rahul V. A1 - Miedema, Piter S. A1 - Schreck, Simon A1 - Quevedo, Wilson A1 - Schröder, Henning A1 - Föhlisch, Alexander A1 - Gaffney, Kelly J. A1 - Lundberg, Marcus A1 - Odelius, Michael A1 - Wernet, Philippe T1 - Viewing the Valence Electronic Structure of Ferric and Ferrous Hexacyanide in Solution from the Fe and Cyanide Perspectives JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - The valence-excited states of ferric and ferrous hexacyanide ions in aqueous solution were mapped by resonant inelastic X-ray scattering (RIXS) at the Fe L-2,L-3 and N K edges. Probing of both the central Fe and the ligand N atoms enabled identification of the metal-and ligand-centered excited states, as well as ligand-to-metal and metal-to-ligand charge-transfer excited states. Ab initio calculations utilizing the RASPT2 method were used to simulate the Fe L-2,L-3-edge RIXS spectra and enabled quantification of the covalencies of both occupied and empty orbitals of pi and sigma symmetry. We found that pi back-donation in the ferric complex is smaller than that in the ferrous complex. This is evidenced by the relative amounts of Fe 3d character in the nominally 2 pi CN- molecular orbital of 7% and 9% in ferric and ferrous hexacyanide, respectively. Utilizing the direct sensitivity of Fe L-3-edge RIXS to the Fe 3d character in the occupied molecular orbitals, we also found that the donation interactions are dominated by sigma bonding. The latter was found to be stronger in the ferric complex, with an Fe 3d contribution to the nominally 5 sigma CN- molecular orbitals of 29% compared to 20% in the ferrous complex. These results are consistent with the notion that a higher charge at the central metal atom increases donation and decreases back-donation. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcb.6b04751 SN - 1520-6106 VL - 120 SP - 7182 EP - 7194 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, Ida A1 - Rajkovic, Ivan A1 - Schreck, Simon A1 - Quevedo, Wilson A1 - Beye, Martin A1 - Grübel, Sebastian A1 - Scholz, Mirko A1 - Nordlund, Dennis A1 - Zhang, Wenkai A1 - Hartsock, Robert W. A1 - Gaffney, Kelly J. A1 - Schlotter, William F. A1 - Turner, Joshua J. A1 - Kennedy, Brian A1 - Hennies, Franz A1 - Techert, Simone A1 - Wernet, Philippe A1 - Odelius, Michael A1 - Föhlisch, Alexander T1 - Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics JF - NEW JOURNAL OF PHYSICS N2 - Ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbital and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)(5) in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given-which will be covered experimentally by upcoming transform-limited x-ray sources. KW - ultrafast photochemistry KW - excited state selectivity KW - anti-Stokes resonant x-ray raman scattering KW - free electron lasers KW - resonant inelastic x-ray scattering Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/10/103011 SN - 1367-2630 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kumph, Muir A1 - Henkel, Carsten A1 - Rabl, Peter A1 - Brownnutt, Michael A1 - Blatt, Rainer T1 - Electric-field noise above a thin dielectric layer on metal electrodes JF - NEW JOURNAL OF PHYSICS N2 - The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electricfield noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps. KW - ion trap KW - electric field noise KW - fluctuation dissipation Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/2/023020 SN - 1367-2630 VL - 18 SP - 1125 EP - 1136 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kuik, Friderike A1 - Lauer, Axel A1 - Churkina, Galina A1 - Van der Gon, Hugo A. C. Denier A1 - Fenner, Daniel A1 - Mar, Kathleen A. A1 - Butler, Tim M. T1 - Air quality modelling in the Berlin-Brandenburg region using WRF-Chem v3.7.1: sensitivity to resolution of model grid and input data JF - Geoscientific model development : an interactive open access journal of the European Geosciences Union N2 - Air pollution is the number one environmental cause of premature deaths in Europe. Despite extensive regulations, air pollution remains a challenge, especially in urban areas. For studying summertime air quality in the Berlin–Brandenburg region of Germany, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) is set up and evaluated against meteorological and air quality observations from monitoring stations as well as from a field campaign conducted in 2014. The objective is to assess which resolution and level of detail in the input data is needed for simulating urban background air pollutant concentrations and their spatial distribution in the Berlin–Brandenburg area. The model setup includes three nested domains with horizontal resolutions of 15, 3 and 1 km and anthropogenic emissions from the TNO-MACC III inventory. We use RADM2 chemistry and the MADE/SORGAM aerosol scheme. Three sensitivity simulations are conducted updating input parameters to the single-layer urban canopy model based on structural data for Berlin, specifying land use classes on a sub-grid scale (mosaic option) and downscaling the original emissions to a resolution of ca. 1 km × 1 km for Berlin based on proxy data including traffic density and population density. The results show that the model simulates meteorology well, though urban 2 m temperature and urban wind speeds are biased high and nighttime mixing layer height is biased low in the base run with the settings described above. We show that the simulation of urban meteorology can be improved when specifying the input parameters to the urban model, and to a lesser extent when using the mosaic option. On average, ozone is simulated reasonably well, but maximum daily 8 h mean concentrations are underestimated, which is consistent with the results from previous modelling studies using the RADM2 chemical mechanism. Particulate matter is underestimated, which is partly due to an underestimation of secondary organic aerosols. NOx (NO + NO2) concentrations are simulated reasonably well on average, but nighttime concentrations are overestimated due to the model's underestimation of the mixing layer height, and urban daytime concentrations are underestimated. The daytime underestimation is improved when using downscaled, and thus locally higher emissions, suggesting that part of this bias is due to deficiencies in the emission input data and their resolution. The results further demonstrate that a horizontal resolution of 3 km improves the results and spatial representativeness of the model compared to a horizontal resolution of 15 km. With the input data (land use classes, emissions) at the level of detail of the base run of this study, we find that a horizontal resolution of 1 km does not improve the results compared to a resolution of 3 km. However, our results suggest that a 1 km horizontal model resolution could enable a detailed simulation of local pollution patterns in the Berlin–Brandenburg region if the urban land use classes, together with the respective input parameters to the urban canopy model, are specified with a higher level of detail and if urban emissions of higher spatial resolution are used. Y1 - 2016 U6 - https://doi.org/10.5194/gmd-9-4339-2016 SN - 1991-959X SN - 1991-9603 VL - 9 SP - 4339 EP - 4363 PB - Copernicus CY - Göttingen ER - TY - THES A1 - Krüsemann, Henning T1 - First passage phenomena and single-file motion in ageing continuous time random walks and quenched energy landscapes N2 - In der Physik gibt es viele Prozesse, die auf Grund ihrer Komplexität nicht durch physikalische Gleichungen beschrieben werden können, beispielsweise die Bewegung eines Staubkorns in der Luft. Durch die vielen Stöße mit Luftmolekülen führt es eine Zufallsbewegung aus, die so genannte Diffusion. Auch Moleküle in biologischen Zellen diffundieren, jedoch befinden sich in einer solchen Zelle im selben Volumen viel mehr oder viel größere Moleküle. Das beobachtete Teilchen stößt dementsprechend öfter mit anderen zusammen und die Diffusion wird langsamer, sie wird subdiffusiv. Mit der Zeit kann sich die Charakteristik der Subdiffusion ändern; dies wird als (mikroskopisches) Altern bezeichnet. Ich untersuche in der vorliegenden Arbeit zwei mathematische Modelle für eindimensionale Subdiffusion, einmal den continuous time random walk (CTRW) und einmal die Zufallsbewegung in einer eingefrorenen Energielandschaft (QEL=quenched energy landscape). Beide sind Sprungprozesse, das heißt, sie sind Abfolgen von räumlichen Sprüngen, die durch zufallsverteilte Wartezeiten getrennt sind. Die Wartezeiten in der QEL sind räumlich korrelliert, während sie im CTRW unkorrelliert sind. Ich untersuche in der vorliegenden Arbeit verschiedene statistische Größen in beiden Modellen. Zunächst untersuche ich den Einfluss des Alters und den Einfluss der Korrellationen einer QEL auf die Verteilung der Zeiten, die das diffundierendes Teilchen benötigt, um eine (räumliche) Schwelle zu überqueren. Ausserdem bestimme ich den Effekt des Alters auf Ströme von (sub)diffundierenden Partikeln, die sich auf eine absorbierende Barriere zubewegen. Zuletzt beschäftige ich mich mit der Diffusion einer eindimensionalen Anordnung von Teilchen in einer QEL, in der diese als harte Kugeln miteinander wechselwirken. Dabei vergleiche ich die gemeinsame Bewegung in einer QEL und als individuelle CTRWs miteinander über die Standartabweichung von der Startposition, für die ich das Mittel über mehrere QELs untersuche. Meine Arbeit setzt sich zusammen aus theoretischen Überlegungen und Berechnungen sowie der Simulation der Zufallsprozesse. Die Ergebnisse der Simulation und, soweit vorhanden, experimentelle Daten werden mit der Theorie verglichen. N2 - In the first part of my work I have investigated the ageing properties of the first passage time distributions in a one-dimensional subdiffusive continuous time random walk with power law distributed waiting times of the form $\psi(\tau) \sim \tau^{-1-\alpha}$ with $0<\alpha<1$ and $1<\alpha<2$. The age or ageing time $t_a$ is the time span from the start of the stochastic process to the start of the observation of this process (at $t=0$). I have calculated the results for a single target and two targets, also including the biased case, where the walker is driven towards the boundary by a constant force. I have furthermore refined the previously derived results for the non-ageing case and investigated the changes that occur when the walk is performed in a discrete quenched energy landscape, where the waiting times are fixed for every site. The results include the exact Laplace space densities and infinite (converging) series as exact results in the time space. The main results are the dominating long time power law behavior regimes, which depend on the ageing time. For the case of unbiased subdiffusion ($\alpha < 1$) in the presence of one target, I find three different dominant terms for ranges of $t$ separated by $t_a$ and another crossover time $t^{\star}$, which depends on $t_a$ as well as on the anomalous exponent $\alpha$ and the anomalous diffusion coefficient $K_{\alpha}$. In all three regimes ($t \ll t_a$, $t_a \ll t \ll t^{\star}$, $t \gg t^{\star}$) one finds power law decay with exponents depending on $\alpha$. The middle regime only exists for $t_a \ll t^{\star}$. The dominant terms in the first two regimes (ageing regimes) come from the probability distribution of the forward waiting time, the time one has to wait for the stochastic process to make the first step during the observation. When the observation time is larger than the second crossover time $t^{\star}$, the first passage time density does not show ageing and the non-ageing first passage time dominates. The power law exponents in the respective regimes are $-\alpha$ for strong ageing, $-1-\alpha$ in the intermediate regime, and $-1-\alpha/2$ in the final non-ageing regime. A similar split into three regimes can be found for $1<\alpha<2$, only with a different second crossover time $t^*$. In this regime the diffusion is normal but also age-dependent. For the diffusion in quenched energy landscapes one cannot detect ageing. The first passage time density shows a quenched power law $^\sim t^{-(1+2\alpha)/(1+\alpha)}$. For diffusion between two target sites and the biased diffusion towards a target only two scaling regimes emerge, separated by the ageing time. In the ageing case $t \ll t_a$ the forward waiting time is again dominant with power law exponent $-\alpha$, while the non-ageing power law $-1-\alpha$ is found for all times $t \gg t_a$. An intermediate regime does not exist. The bias and the confinement have similar effects on the first passage time density. For quenched diffusion, the biased case is interesting, as the bias reduces correlations due to revisiting of the same waiting time. As a result, CTRW like behavior is observed, including ageing. Extensive computer simulations support my findings. The second part of my research was done on the subject of ageing Scher-Montroll transport, which is in parts closely related to the first passage densities. It explains the electrical current in an amorphous material. I have investigated the effect of the width of a given initial distribution of charge carriers on the transport coefficients as well as the ageing effect on the emerging power law regimes and a constant initial regime. While a spread out initial distribution has only little impact on the Scher-Montroll current, ageing alters the behavior drastically. Instead of the two classical power laws one finds four current regimes, up to three of which can appear in a single experiment. The dominant power laws differ for $t \ll t_a, t_c$, $t_a \ll t \ll t_c$, $t_c \ll t \ll t_a$, and $t \gg t_a,t_c$. Here, $t_c$ is the crossover time of the non-aged Scher-Montroll current. For strongly aged systems one can observe a constant current in the first regime while the others are dominated by decaying power laws with exponents $\alpha -1$, $-\alpha$, and $-1-\alpha$. The ageing regimes are the 1st and 3rd one, while the classical regimes are the 2nd and the 4th. I have verified the theory using numerical integration of the exact integrals and applied the new results to experimental data. In the third part I considered a single file of subdiffusing particles in an energy landscape. Every occupied site of the landscape acts as a boundary, from which a particle is immediately reflected to its previous site, if it tries to jump there. I have analysed the effects single-file diffusion a quenched landscape compared to an annealed landscape and I have related these results to the number of steps and related quantities. The diffusion changes from ultraslow logarithmic diffusion in the annealed or CTRW case to subdiffusion with an anomalous exponent $\alpha/(1+\alpha)$ in the quenched landscape. The behavior is caused by the forward waiting time, which changes drastically from the quenched to the annealed case. Single-file effects in the quenched landscape are even more complicated to consider in the ensemble average, since the diffusion in individual landscapes shows extremely diverse behavior. Extensive simulations support my theoretical arguments, which consider mainly the long time evolution of the mean square displacement of a bulk particle. KW - continuous time random walk KW - quenched energy landscape KW - first passage time KW - Scher-Montroll transport KW - single-file motion KW - Zufallsbewegung KW - Diffusion KW - eingefrorene Energielandschaft KW - Scher-Montroll Transport KW - Wartezeitverteilung Y1 - 2016 ER - TY - JOUR A1 - Kruesemann, Henning A1 - Schwarzl, Richard A1 - Metzler, Ralf T1 - Ageing Scher-Montroll Transport JF - Transport in Porous Media N2 - We study the properties of ageing Scher-Montroll transport in terms of a biased subdiffusive continuous time random walk in which the waiting times between consecutive jumps of the charge carriers are distributed according to the power law probability with . As we show, the dynamical properties of the Scher-Montroll transport depend on the ageing time span between the initial preparation of the system and the start of the observation. The Scher-Montroll transport theory was originally shown to describe the photocurrent in amorphous solids in the presence of an external electric field, but it has since been used in many other fields of physical sciences, in particular also in the geophysical context for the description of the transport of tracer particles in subsurface aquifers. In the absence of ageing () the photocurrent of the classical Scher-Montroll model or the breakthrough curves in the groundwater context exhibit a crossover between two power law regimes in time with the scaling exponents and . In the presence of ageing a new power law regime and an initial plateau regime of the current emerge. We derive the different power law regimes and crossover times of the ageing Scher-Montroll transport and show excellent agreement with simulations of the process. Experimental data of ageing Scher-Montroll transport in polymeric semiconductors are shown to agree well with the predictions of our theory. KW - Anomalous diffusion KW - Ageing KW - Scher-Montroll transport Y1 - 2016 U6 - https://doi.org/10.1007/s11242-016-0686-y SN - 0169-3913 SN - 1573-1634 VL - 115 SP - 327 EP - 344 PB - Springer CY - New York ER - TY - JOUR A1 - Kronberg, Elena A. A1 - Rashev, M. V. A1 - Daly, P. W. A1 - Shprits, Yuri Y. A1 - Turner, D. L. A1 - Drozdov, Alexander A1 - Dobynde, M. A1 - Kellerman, Adam C. A1 - Fritz, T. A. A1 - Pierrard, V. A1 - Borremans, K. A1 - Klecker, B. A1 - Friedel, R. T1 - Contamination in electron observations of the silicon detector on board JF - Space Weather: The International Journal of Research and Applications N2 - Since more than 15 years, the Cluster mission passes through Earth's radiation belts at least once every 2 days for several hours, measuring the electron intensity at energies from 30 to 400 keV. These data have previously been considered not usable due to contamination caused by penetrating energetic particles (protons at >100 keV and electrons at >400 keV). In this study, we assess the level of distortion of energetic electron spectra from the Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector, determining the efficiency of its shielding. We base our assessment on the analysis of experimental data and a radiation transport code (Geant4). In simulations, we use the incident particle energy distribution of the AE9/AP9 radiation belt models. We identify the Roederer L values, L⋆, and energy channels that should be used with caution: at 3≤L⋆≤4, all energy channels (40–400 keV) are contaminated by protons (≃230 to 630 keV and >600 MeV); at L⋆≃1 and 4–6, the energy channels at 95–400 keV are contaminated by high-energy electrons (>400 keV). Comparison of the data with electron and proton observations from RBSP/MagEIS indicates that the subtraction of proton fluxes at energies ≃ 230–630 keV from the IES electron data adequately removes the proton contamination. We demonstrate the usefulness of the corrected data for scientific applications. Y1 - 2016 U6 - https://doi.org/10.1002/2016SW001369 SN - 1542-7390 VL - 14 SP - 449 EP - 462 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Kroll, Thomas A1 - Kern, Jan A1 - Kubin, Markus A1 - Ratner, Daniel A1 - Gul, Sheraz A1 - Fuller, Franklin D. A1 - Löchel, Heike A1 - Krzywinski, Jacek A1 - Lutman, Alberto A1 - Ding, Yuantao A1 - Dakovski, Georgi L. A1 - Moeller, Stefan A1 - Turner, Joshua J. A1 - Alonso-Mori, Roberto A1 - Nordlund, Dennis L. A1 - Rehanek, Jens A1 - Weniger, Christian A1 - Firsov, Alexander A1 - Brzhezinskaya, Maria A1 - Chatterjee, Ruchira A1 - Lassalle-Kaiser, Benedikt A1 - Sierra, Raymond G. A1 - Laksmono, Hartawan A1 - Hill, Ethan A1 - Borovik, Andrew S. A1 - Erko, Alexei A1 - Föhlisch, Alexander A1 - Mitzner, Rolf A1 - Yachandra, Vittal K. A1 - Yano, Junko A1 - Wernet, Philippe A1 - Bergmann, Uwe T1 - X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser JF - Optics express : the international electronic journal of optics N2 - X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements. (C) 2016 Optical Society of America Y1 - 2016 U6 - https://doi.org/10.1364/OE.24.022469 SN - 1094-4087 VL - 24 SP - 22469 EP - 22480 PB - Optical Society of America CY - Washington ER - TY - JOUR A1 - Kretschmer, Marlene A1 - Coumou, Dim A1 - Donges, Jonathan A1 - Runge, Jakob T1 - Using Causal Effect Networks to Analyze Different Arctic Drivers of Midlatitude Winter Circulation JF - Journal of climate N2 - In recent years, the Northern Hemisphere midlatitudes have suffered from severe winters like the extreme 2012/13 winter in the eastern United States. These cold spells were linked to a meandering upper-tropospheric jet stream pattern and a negative Arctic Oscillation index (AO). However, the nature of the drivers behind these circulation patterns remains controversial. Various studies have proposed different mechanisms related to changes in the Arctic, most of them related to a reduction in sea ice concentrations or increasing Eurasian snow cover. Here, a novel type of time series analysis, called causal effect networks (CEN), based on graphical models is introduced to assess causal relationships and their time delays between different processes. The effect of different Arctic actors on winter circulation on weekly to monthly time scales is studied, and robust network patterns are found. Barents and Kara sea ice concentrations are detected to be important external drivers of the midlatitude circulation, influencing winter AO via tropospheric mechanisms and through processes involving the stratosphere. Eurasia snow cover is also detected to have a causal effect on sea level pressure in Asia, but its exact role on AO remains unclear. The CEN approach presented in this study overcomes some difficulties in interpreting correlation analyses, complements model experiments for testing hypotheses involving teleconnections, and can be used to assess their validity. The findings confirm that sea ice concentrations in autumn in the Barents and Kara Seas are an important driver of winter circulation in the midlatitudes. Y1 - 2016 U6 - https://doi.org/10.1175/JCLI-D-15-0654.1 SN - 0894-8755 SN - 1520-0442 VL - 29 SP - 4069 EP - 4081 PB - American Meteorological Soc. CY - Boston ER - TY - JOUR A1 - Kopyshev, Alexey A1 - Galvin, Casey J. A1 - Patil, Rohan R. A1 - Genzer, Jan A1 - Lomadze, Nino A1 - Feldmann, David A1 - Zakrevski, Juri A1 - Santer, Svetlana T1 - Light-Induced Reversible Change of Roughness and Thickness of Photosensitive Polymer Brushes JF - Applied physics : A, Materials science & processing N2 - We investigate light-induced changes in thickness and roughness of photosensitive polymer brushes containing azobenzene cationic surfactants by atomic force microscopy (AFM) in real time during light irradiation. Because the cis-state of azobenzene unit requires more free volume than its trans counterpart, the UV light-induced expansion of polymer thin films associated with the trans-to-cis isomerism of azobenzene groups is expected to occur. This phenomenon is well documented in physisorbed polymer films containing azobenzene groups. In contrast, photosensitive polymer brushes show a decrease in thickness under UV irradiation. We have found that the azobenzene surfactants in their trans-state form aggregates within the brush. Under irradiation, the surfactants undergo photoisomerization to the cis-state, which is more hydrophilic. As a consequence, the aggregates within the brush are disrupted, and the polymer brush contracts. When subsequently irradiated with blue light the polymer brush thickness returns back to its initial value. This behavior is related to isomerization of the surfactant to the more hydrophobic trans-state and subsequent formation of surfactant aggregates within the polymer brush. The photomechanical function of the dry polymer brush, i.e., contraction and expansion, was found to be reversible with repeated irradiation cycles and requires only a few seconds for switching. In addition to the thickness change, the roughness of the brush also changes reversibly between a few Angstroms (blue light) and several nanometers (UV light). Photosensitive polymer brushes represent smart films with light responsive thickness and roughness that could be used for generating dynamic fluctuating surfaces, the function of which can be turned on and off in a controllable manner on a nanometer length scale. KW - photosensitive brushes KW - azobenzene containing surfactants KW - light driven reversible change of surface topography and thickness KW - domain memory in polymer brushes KW - orientation of azobenzenes in polymer brushes Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b06881 SN - 1944-8244 VL - 8 SP - 19175 EP - 19184 PB - American Chemical Society CY - Washington ER -