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 -