TY - JOUR A1 - Assagra, Yuri A.O. A1 - Altafim, Ruy Alberto Pisani A1 - do Carmo, Joao P. A1 - Altafim, Ruy A.C. A1 - Rychkov, Dmitry A1 - Wirges, Werner A1 - Gerhard, Reimund T1 - A new route to piezo-polymer transducers: 3D printing of polypropylene ferroelectrets JF - IEEE transactions on dielectrics and electrical insulation N2 - Here, a promising approach for producing piezo-polymer transducers in a one-step process is presented. Using 3D-printing technology and polypropylene (PP) filaments, we are able to print a two-layered film structure with regular cavities of precisely controlled size and shape. It is found that the 3D-printed samples exhibit piezoelectric coefficients up to 200 pC/N, similar to those of other PP ferroelectrets, and their temporal and thermal behavior is in good agreement with those known of PP ferroelectrets. The piezoelectric response strongly decreases for applied pressures above 20 kPa, as the pressure in the air-filled cavities strongly influences the overall elastic modulus of ferroelectrets. KW - 3D printing KW - polymer ferroelectrets KW - sensors and actuators KW - piezoelectrets KW - electret polymers KW - soft electro-active materials KW - functional materials KW - soft matter Y1 - 2020 U6 - https://doi.org/10.1109/TDEI.2020.008461 SN - 1070-9878 SN - 1558-4135 VL - 27 IS - 5 SP - 1668 EP - 1674 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER - TY - JOUR A1 - Awad, Emad A1 - Metzler, Ralf T1 - Crossover dynamics from superdiffusion to subdiffusion BT - models and solutions JF - Fractional calculus and applied analysis : an international journal for theory and applications N2 - The Cattaneo or telegrapher's equation describes the crossover from initial ballistic to normal diffusion. Here we study and survey time-fractional generalisations of this equation that are shown to produce the crossover of the mean squared displacement from superdiffusion to subdiffusion. Conditional solutions are derived in terms of Fox H-functions and the dth-order moments as well as the diffusive flux of the different models are derived. Moreover, the concept of the distribution-like is proposed as an alternative to the probability density function. KW - Cattaneo equation KW - telegrapher's equation KW - crossover dynamics KW - fractional dynamic equations KW - anomalous diffusion KW - superdiffusion and KW - subdiffusion KW - Fox H-functions Y1 - 2020 U6 - https://doi.org/10.1515/fca-2020-0003 SN - 1311-0454 SN - 1314-2224 VL - 23 IS - 1 SP - 55 EP - 102 PB - De Gruyter CY - Berlin ; Boston ER - TY - JOUR A1 - Bouakline, Foudhil T1 - Does nuclear permutation symmetry allow dynamical localization in symmetric double-well achiral molecules? JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - We discuss the effect of molecular symmetry on coherent tunneling in symmetric double-well potentials whose two molecular equilibrium configurations are interconverted by nuclear permutations. This is illustrated with vibrational tunneling in ammonia molecules, electronic tunneling in the dihydrogen cation, and laser-induced rotational tunneling of homonuclear diatomics. In this contribution, we reexamine the textbook picture of coherent tunneling in such potentials, which is depicted with a wavepacket shuttling back and forth between the two potential-wells. We show that the common application of this picture to the aforementioned molecules contravenes the principle of the indistinguishability of identical particles. This conflict originates from the sole consideration of the dynamics of the tunneling-mode, connecting the double-well energy minima, and complete omission of all the remaining molecular degrees of freedom. This gives rise to double-well wavepackets that are nonsymmetric under nuclear permutations. To obey quantum statistics, we show that the double-well eigenstates composing these wavepackets must be entangled with the wavefunctions that describe all the omitted molecular modes. These wavefunctions have compensating and opposite nuclear permutation symmetry. This in turn leads to complete quenching of interference effects behind localization in one potential-well or another. Indeed, we demonstrate that the reduced density of probability of the symmetrized molecular wavefunction, where all the molecular coordinates but the tunneling-mode are integrated out, is symmetrically distributed over the two potential-wells, at all times. This applies to any multilevel wavepacket of isotropic or fully aligned symmetric double-well achiral molecules. However, in the case of coherent electronic or vibrational tunneling, fully aligned molecules may exhibit dynamical localization in the space-fixed frame, where the tunneling-mode density shuttles between the opposite directions of the alignment axis. This dynamical spatial-localization results from linear combinations of molecular states that have opposite parity. In summary, this study shows that dynamical localization of the tunneling-mode density on either of the two indistinguishable molecular equilibrium configurations of symmetric double-well achiral molecules is forbidden by quantum statistics, whereas its dynamical localization in the space-fixed frame is allowed by parity. The subtle distinction between these two types of localization has far-reaching implications in the interpretation of many ultrafast molecular dynamics experiments. Y1 - 2020 U6 - https://doi.org/10.1063/1.5141746 SN - 0021-9606 SN - 1089-7690 VL - 152 IS - 24 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Brose, Robert T1 - From dawn till dusk BT - modelling particle acceleration in supernova remnants N2 - Supernova remnants are believed to be the source of cosmic rays with energies up to 10^15 eV that are produced within our Galaxy. The acceleration mechanism associated with the collision-less shocks in supernova remnants - diffusive shock acceleration - predicts a spectral index of the accelerated non-thermal particles of s = 2. However, measurements of non-thermal emission in radio, X-rays and gamma-rays reveal significant deviations of the particles spectral index from the canonical value of s = 2. The youngest Galactic supernova remnant G1.9+0.3 is an interesting target for next-generation gamma-ray observatories. So far, the remnant is only detected in the radio and the X-ray bands, but its young age of ≈100 yrs and inferred shock speed of ≈ 14, 000 km/s could make it an efficient particle accelerator. I performed spherical symmetric 1D simulations with the RATPaC code, in which I simultaneously solved the transport equation for cosmic rays, the transport equation for magnetic turbulence, and the hydro-dynamical equations for the gas flow. Separately computed distributions of the particles accelerated at the forward and the reverse shock were then used to calculate the spectra of synchrotron, inverse Compton, and Pion-decay radiation from the source. The emission from G1.9+0.3 can be self-consistently explained within the test-particle limit. I find that the X-ray flux is dominated by emission from the forward shock while most of the radio emission originates near the reverse shock, which makes G1.9+0.3 the first remnant with non-thermal radiation detected from the reverse shock. The flux of very-high-energy gamma-ray emission from G1.9+0.3 is expected to be close to the sensitivity threshold of the Cherenkov Telescope Array. The limited time available to grow large-scale turbulence limits the maximum energy of particles to values below 100 TeV, hence G1.9+0.3 is not a PeVatron. Although there are many models for the acceleration of cosmic rays in Supernova remnants, the escape of cosmic rays from these sources is yet understudied. I use our time-dependent acceleration code RATPaC to study the acceleration of cosmic rays and their escape in post-adiabatic Supernova remnants and calculate the subsequent gamma-ray emission from inverse-Compton scattering and Pion decay. My simulations span 100,000 years, thus covering the free-expansion, the Sedov-Taylor, and the beginning of the post-adiabatic phase of the remnant’s evolution. At later stages of the evolution cosmic rays over a wide range of energy can reside outside of the remnant, creating spectra that are softer than predicted by standard diffusive shock acceleration and feature breaks in the 10 - 100 GeV-range. The total spectrum of cosmic rays released into the interstellar medium has a spectral index of s ≈ 2.4 above roughly 10 GeV which is close to that required by Galactic propagation models. I further find the gamma-ray luminosity to peak around an age of 4,000 years for inverse-Compton-dominated high-energy emission. Remnants expanding in low-density media emit generally more inverse-Compton radiation matching the fact that the brightest known supernova remnants - RCW86, Vela Jr, HESSJ1721-347 and RXJ1713.7-3946 - are all expanding in low density environments. The importance of feedback from the cosmic-rays on the hydrodynamical evolution of the remnants is debated as a possibility to obtain soft cosmic-ray spectra at low energies. I performed spherically symmetric 1-D simulations with a modified version of the RATPaC code, in which I simultaneously solve the transport equation for cosmic rays and the hydrodynamical equations, including the back-reaction of the cosmic-ray pressure on the flow profiles. Besides the known modification of the flow profiles and the consequently curved cosmic-ray spectra, steady-state models for non-linear diffusive shock acceleration overpredict the total compression ratio that can be reached with cosmic-ray feedback, as there is limited time for building these modifications. Further, I find modifications to the downstream flow structure that change the evolutionary behavior of the remnant and trigger a cosmic-ray-induced instability close to the contact discontinuity, if and when the cosmic-ray pressure becomes dominant there. N2 - Es wird vermutet das Supernovaüberreste die Quelle der galaktischen kosmischen Strahlung mit Energien bis zu 10^15eV sein können. Der Beschleunigungsprozess der mit den kollisionsfreien Schocks in Supernovaüberresten in Verbindung gebracht wird - diffuse Schockwellenbeschleunigung - sagt nicht-thermische Teilchenspektren mit einem Spektralindex von s=2 voraus. Messungen nicht-thermischer Strahlung im Radio-, Röntgen- und Gammastrahlenbereich zeigen teils deutliche Abweichungen von dieser Vorhersage. Der jüngste galaktische Supernovaüberrest G1.9+0.3 ist ein interessantes Ziel für zukünftige Gammastrahlenteleskope. Bis jetzt wurde der Überrest nur im Radio- und Röntgenband entdeckt aber sein geringes Alter von ~100 Jahren und die gemessenen hohen Schockgeschwindigkeiten von ~14,000km/s sollten Teilchenbeschleunigung auch bis zu sehr hohen Energien ermöglichen. In dieser Arbeit wurden 1D-Simulationen der Teilchenbeschleunigung in G1.9+0.3 mit Hilfe der RATPaC-Programmbibliothek durchgeführt, wobei das System der gekoppelten Differentialgleichungen für den Teilchentransport, den Transport der magnetischen Turbulenz und der Standardgasgleichungen gelöst wurde. Die separat berechneten Verteilungen der Teilchen an Vorwärts- und Rückwärtsschock wurden benutzt um die Emission des Überrests im Radio-, Röntgen und Gammastrahlungsbereich zu bestimmen. Die Emissionen von G1.9+0.3 können selbst konsistent in der Testteilchennäherung bestimmt werden. Die Röntgenemission wird vom Vorwärtsschock dominiert, während die Radioemissionen hauptsächlich vom Rückwätsschock stammen. Dies macht G1.9+0.3 zum ersten Überrest mit detektierter nich-thermischer Strahlung aus dem Bereich des Rückwärtsschocks. Die erwartet Gammastrahlungsemission ist nahe dem Detektionslimit des zukünftigen Cherenkov Telescope Arrays. Die geringe Alter von G1.9+0.3 begrenzt die Maximalenergie, die im Beschleunigungsprozess erreicht werden kann auf Werte unterhalb von 100TeV. Demnach ist G1.9+0.3 kein PeVatron. Auch wenn es zahlreiche Modelle zur Teilchenbeschleunigung in Supernovaüberresten gibt, ist das Entkommen der Teilchen aus den Überresten zur Zeit wenig erforscht. Mit Hilfe von RATPaC haben wir die Evolution und Teilchenbeschleunigung in Supernovaüberresten über 100,000 Jahre simuliert. Dieser Zeitraum deckt einen Großteil der Lebensspanne eines Supernovaüberrests ab und endet mit der letzten Teil der postadiabatischen Phase der Entwicklung des Überrests. In den späten Phasen der Entwicklung des Überrests können Teilchen in einem großen Energiebereich aus dem Überrest entweichen. Dies erzeugt Emissionspektren, die weicher sind als durch Fermibeschleunigung vorhergesagt, und die spektrale Brüche im Bereich von 10-100GeV aufweisen. Das Produktionsspektren der Überreste hat einen spektralen Index von s~2.4 oberhalb von 10GeV, was ungefähr mit den Spektren übereinstimmt, die Quellen in galaktischen Propagationsmodellen aufweisen müssen. Weiterhin erreichen die Überreste ihre größte Helligkeit im Gammabereich nach etwa 4000 Jahren wenn diese durch inverse Comptonstreuung erzeugt werden. Dabei erreichen Überreste in Medien mit geringer Umgebungsdichte größere Helligkeiten, was sich mit den Beobachtungen der hellsten Supernovaüberreste - RCW86, Vela Jr., HESSJ1721-347 und RXJ1713.7-3946 - deckt, die alle in Bereichen sehr geringer Umgebungsdichte expandieren. In der Literatur wird die Möglichkeit diskutiert, dass die Rückkopplung der Beschleunigten Teilchen auf die Struktur der Überreste für die beobachteten weichen Strahlungsspektren verantwortlich ist. Im Rahmen dieser Arbeit wurde eine modifizierte Version von RATPaC entwickelt, die diesen Prozess abbilden kann. Neben den bekannten Rückkopplungen zeigt sich, dass bisherige Modelle unter der Annahme eines Gleichgewichtszustandes für die beschleunigten Teilchen die erreicht maximal Kompression des Plasmas durch den Schock und damit die Härte der Teilchenspektren überschätzen. In unseren zeit aufgelösten Berechnungen ist die maximale Kompression durch die limitierte verfügbare Zeit begrenzt. Zusätzlich zeigt sich das Auftreten einer Instabilität die durch die Rückkopplung der kosmischen Strahlung nahe der Kontaktdiskontinuität hervorgerufen wird. KW - supernova remnant KW - particle acceleration KW - gamma rays KW - Supernovaüberrest KW - Teilchenbeschleunigung KW - Gammastrahlung Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-470865 ER - TY - JOUR A1 - Cabalar, Pedro A1 - Fandiño, Jorge A1 - Lierler, Yuliya T1 - Modular Answer Set Programming as a formal specification language JF - Theory and practice of logic programming N2 - In this paper, we study the problem of formal verification for Answer Set Programming (ASP), namely, obtaining aformal proofshowing that the answer sets of a given (non-ground) logic programPcorrectly correspond to the solutions to the problem encoded byP, regardless of the problem instance. To this aim, we use a formal specification language based on ASP modules, so that each module can be proved to capture some informal aspect of the problem in an isolated way. This specification language relies on a novel definition of (possibly nested, first order)program modulesthat may incorporate local hidden atoms at different levels. Then,verifyingthe logic programPamounts to prove some kind of equivalence betweenPand its modular specification. KW - Answer Set Programming KW - formal specification KW - formal verification KW - modular logic programs Y1 - 2020 U6 - https://doi.org/10.1017/S1471068420000265 SN - 1471-0684 SN - 1475-3081 VL - 20 IS - 5 SP - 767 EP - 782 PB - Cambridge University Press CY - New York ER - TY - GEN A1 - Caesar, Levke A1 - Rahmstorf, Stefan A1 - Feulner, Georg T1 - On the relationship between Atlantic meridional overturning circulation slowdown and global surface warming T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - According to established understanding, deep-water formation in the North Atlantic and Southern Ocean keeps the deep ocean cold, counter-acting the downward mixing of heat from the warmer surface waters in the bulk of the world ocean. Therefore, periods of strong Atlantic meridional overturning circulation (AMOC) are expected to coincide with cooling of the deep ocean and warming of the surface waters. It has recently been proposed that this relation may have reversed due to global warming, and that during the past decades a strong AMOC coincides with warming of the deep ocean and relative cooling of the surface, by transporting increasingly warmer waters downward. Here we present multiple lines of evidence, including a statistical evaluation of the observed global mean temperature, ocean heat content, and different AMOC proxies, that lead to the opposite conclusion: even during the current ongoing global temperature rise a strong AMOC warms the surface. The observed weakening of the AMOC has therefore delayed global surface warming rather than enhancing it. Social Media Abstract: The overturning circulation in the Atlantic Ocean has weakened in response to global warming, as predicted by climate models. Since it plays an important role in transporting heat, nutrients and carbon, a slowdown will affect global climate processes and the global mean temperature. Scientists have questioned whether this slowdown has worked to cool or warm global surface temperatures. This study analyses the overturning strength and global mean temperature evolution of the past decades and shows that a slowdown acts to reduce the global mean temperature. This is because a slower overturning means less water sinks into the deep ocean in the subpolar North Atlantic. As the surface waters are cold there, the sinking normally cools the deep ocean and thereby indirectly warms the surface, thus less sinking implies less surface warming and has a cooling effect. For the foreseeable future, this means that the slowing of the overturning will likely continue to slightly reduce the effect of the general warming due to increasing greenhouse gas concentrations. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1426 KW - Atlantic meridional overturning circulation KW - global surface warming KW - ocean heat uptake Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-512382 SN - 1866-8372 IS - 2 ER - TY - JOUR A1 - Caesar, Levke A1 - Rahmstorf, Stefan A1 - Feulner, Georg T1 - On the relationship between Atlantic meridional overturning circulation slowdown and global surface warming JF - Environmental research letters N2 - According to established understanding, deep-water formation in the North Atlantic and Southern Ocean keeps the deep ocean cold, counter-acting the downward mixing of heat from the warmer surface waters in the bulk of the world ocean. Therefore, periods of strong Atlantic meridional overturning circulation (AMOC) are expected to coincide with cooling of the deep ocean and warming of the surface waters. It has recently been proposed that this relation may have reversed due to global warming, and that during the past decades a strong AMOC coincides with warming of the deep ocean and relative cooling of the surface, by transporting increasingly warmer waters downward. Here we present multiple lines of evidence, including a statistical evaluation of the observed global mean temperature, ocean heat content, and different AMOC proxies, that lead to the opposite conclusion: even during the current ongoing global temperature rise a strong AMOC warms the surface. The observed weakening of the AMOC has therefore delayed global surface warming rather than enhancing it. Social Media Abstract: The overturning circulation in the Atlantic Ocean has weakened in response to global warming, as predicted by climate models. Since it plays an important role in transporting heat, nutrients and carbon, a slowdown will affect global climate processes and the global mean temperature. Scientists have questioned whether this slowdown has worked to cool or warm global surface temperatures. This study analyses the overturning strength and global mean temperature evolution of the past decades and shows that a slowdown acts to reduce the global mean temperature. This is because a slower overturning means less water sinks into the deep ocean in the subpolar North Atlantic. As the surface waters are cold there, the sinking normally cools the deep ocean and thereby indirectly warms the surface, thus less sinking implies less surface warming and has a cooling effect. For the foreseeable future, this means that the slowing of the overturning will likely continue to slightly reduce the effect of the general warming due to increasing greenhouse gas concentrations. KW - Atlantic meridional overturning circulation KW - global surface warming KW - ocean heat uptake Y1 - 2020 U6 - https://doi.org/10.1088/1748-9326/ab63e3 SN - 1748-9326 VL - 15 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Caetano, Daniel L. Z. A1 - Carvalho, Sidney Jurado de A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of multiple polyelectrolytes onto a nanosphere BT - splitting the adsorption-desorption transition boundary JF - Interface : journal of the Royal Society N2 - Employing extensive Monte Carlo computer simulations, we investigate in detail the properties of multichain adsorption of charged flexible polyelectrolytes (PEs) onto oppositely charged spherical nanoparticles (SNPs). We quantify the conditions of critical adsorption-the phase-separation curve between the adsorbed and desorbed states of the PEs-as a function of the SNP surface-charge density and the concentration of added salt. We study the degree of fluctuations of the PE-SNP electrostatic binding energy, which we use to quantify the emergence of the phase subtransitions, including a series of partially adsorbed PE configurations. We demonstrate how the phase-separation adsorption-desorption boundary shifts and splits into multiple subtransitions at low-salt conditions, thereby generalizing and extending the results for critical adsorption of a single PE onto the SNP. The current findings are relevant for finite concentrations of PEs around the attracting SNP, such as the conditions for PE adsorption onto globular proteins carrying opposite electric charges. KW - nanoparticles KW - polyelectrolytes KW - electrostatics KW - critical adsorption KW - phase-transition boundary Y1 - 2020 U6 - https://doi.org/10.1098/rsif.2020.0199 SN - 1742-5689 SN - 1742-5662 VL - 17 IS - 167 PB - Royal Society CY - London ER - TY - JOUR A1 - Capała, Karol A1 - Padash, Amin A1 - Chechkin, Aleksei V. A1 - Shokri, Babak A1 - Metzler, Ralf A1 - Dybiec, Bartłomiej T1 - Levy noise-driven escape from arctangent potential wells JF - Chaos : an interdisciplinary journal of nonlinear science N2 - The escape from a potential well is an archetypal problem in the study of stochastic dynamical systems, representing real-world situations from chemical reactions to leaving an established home range in movement ecology. Concurrently, Levy noise is a well-established approach to model systems characterized by statistical outliers and diverging higher order moments, ranging from gene expression control to the movement patterns of animals and humans. Here, we study the problem of Levy noise-driven escape from an almost rectangular, arctangent potential well restricted by two absorbing boundaries, mostly under the action of the Cauchy noise. We unveil analogies of the observed transient dynamics to the general properties of stationary states of Levy processes in single-well potentials. The first-escape dynamics is shown to exhibit exponential tails. We examine the dependence of the escape on the shape parameters, steepness, and height of the arctangent potential. Finally, we explore in detail the behavior of the probability densities of the first-escape time and the last-hitting point. Y1 - 2020 U6 - https://doi.org/10.1063/5.0021795 SN - 1054-1500 SN - 1089-7682 VL - 30 IS - 12 PB - American Institute of Physics CY - Woodbury, NY ER - TY - JOUR A1 - Cervantes Villa, Juan Sebastian A1 - Shprits, Yuri Y. A1 - Aseev, Nikita A1 - Allison, Hayley J. T1 - Quantifying the effects of EMIC wave scattering and magnetopause shadowing in the outer electron radiation belt by means of data assimilation JF - Journal of geophysical research : Space physics N2 - In this study we investigate two distinct loss mechanisms responsible for the rapid dropouts of radiation belt electrons by assimilating data from Van Allen Probes A and B and Geostationary Operational Environmental Satellites (GOES) 13 and 15 into a 3-D diffusion model. In particular, we examine the respective contribution of electromagnetic ion cyclotron (EMIC) wave scattering and magnetopause shadowing for values of the first adiabatic invariant mu ranging from 300 to 3,000 MeV G(-1). We inspect the innovation vector and perform a statistical analysis to quantitatively assess the effect of both processes as a function of various geomagnetic indices, solar wind parameters, and radial distance from the Earth. Our results are in agreement with previous studies that demonstrated the energy dependence of these two mechanisms. We show that EMIC wave scattering tends to dominate loss at lower L shells, and it may amount to between 10%/hr and 30%/hr of the maximum value of phase space density (PSD) over all L shells for fixed first and second adiabatic invariants. On the other hand, magnetopause shadowing is found to deplete electrons across all energies, mostly at higher L shells, resulting in loss from 50%/hr to 70%/hr of the maximum PSD. Nevertheless, during times of enhanced geomagnetic activity, both processes can operate beyond such location and encompass the entire outer radiation belt. Y1 - 2020 U6 - https://doi.org/10.1029/2020JA028208 SN - 2169-9380 SN - 2169-9402 VL - 125 IS - 8 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Chen, Cong A1 - Müller, Bernd R. A1 - Prinz, Carsten A1 - Stroh, Julia A1 - Feldmann, Ines A1 - Bruno, Giovanni T1 - The correlation between porosity characteristics and the crystallographic texture in extruded stabilized aluminium titanate for diesel particulate filter applications JF - Journal of the European Ceramic Society N2 - Porous ceramic diesel particulate filters (DPFs) are extruded products that possess macroscopic anisotropic mechanical and thermal properties. This anisotropy is caused by both morphological features (mostly the orientation of porosity) and crystallographic texture. We systematically studied those two aspects in two aluminum titanate ceramic materials of different porosity using mercury porosimetry, gas adsorption, electron microscopy, X-ray diffraction, and X-ray refraction radiography. We found that a lower porosity content implies a larger isotropy of both the crystal texture and the porosity orientation. We also found that, analogous to cordierite, crystallites do align with their axis of negative thermal expansion along the extrusion direction. However, unlike what found for cordierite, the aluminium titanate crystallite form is such that a more pronounced (0 0 2) texture along the extrusion direction implies porosity aligned perpendicular to it. KW - preferred orientation KW - X-ray refraction KW - pore orientation KW - crystal KW - structure KW - extrusion KW - microstructure-property relations Y1 - 2020 U6 - https://doi.org/10.1016/j.jeurceramsoc.2019.11.076 SN - 0955-2219 SN - 1873-619X VL - 40 IS - 4 SP - 1592 EP - 1601 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Chen, Junchao A1 - Lange, Thomas A1 - Andjelkovic, Milos A1 - Simevski, Aleksandar A1 - Krstić, Miloš T1 - Prediction of solar particle events with SRAM-based soft error rate monitor and supervised machine learning JF - Microelectronics reliability N2 - This work introduces an embedded approach for the prediction of Solar Particle Events (SPEs) in space applications by combining the real-time Soft Error Rate (SER) measurement with SRAM-based detector and the offline trained machine learning model. The proposed approach is intended for the self-adaptive fault-tolerant multiprocessing systems employed in space applications. With respect to the state-of-the-art, our solution allows for predicting the SER 1 h in advance and fine-grained hourly tracking of SER variations during SPEs as well as under normal conditions. Therefore, the target system can activate the appropriate mechanisms for radiation hardening before the onset of high radiation levels. Based on the comparison of five different machine learning algorithms trained with the public space flux database, the preliminary results indicate that the best prediction accuracy is achieved with the recurrent neural network (RNN) with long short-term memory (LSTM). Y1 - 2020 U6 - https://doi.org/10.1016/j.microrel.2020.113799 SN - 0026-2714 VL - 114 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Cheng, Xin A1 - Zhang, Jie A1 - Kliem, Bernhard A1 - Török, Tibor A1 - Xing, Chen A1 - Zhou, Zhenjun A1 - Inhester, Bernd A1 - Ding, Mingde T1 - Initiation and early kinematic evolution of solar eruptions T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - We investigate the initiation and early evolution of 12 solar eruptions, including six active-region hot channel and six quiescent filament eruptions, which were well observed by the Solar Dynamics Observatory, as well as by the Solar Terrestrial Relations Observatory for the latter. The sample includes one failed eruption and 11 coronal mass ejections, with velocities ranging from 493 to 2140 km s(-1). A detailed analysis of the eruption kinematics yields the following main results. (1) The early evolution of all events consists of a slow-rise phase followed by a main-acceleration phase, the height-time profiles of which differ markedly and can be best fit, respectively, by a linear and an exponential function. This indicates that different physical processes dominate in these phases, which is at variance with models that involve a single process. (2) The kinematic evolution of the eruptions tends to be synchronized with the flare light curve in both phases. The synchronization is often but not always close. A delayed onset of the impulsive flare phase is found in the majority of the filament eruptions (five out of six). This delay and its trend to be larger for slower eruptions favor ideal MHD instability models. (3) The average decay index at the onset heights of the main acceleration is close to the threshold of the torus instability for both groups of events (although, it is based on a tentative coronal field model for the hot channels), suggesting that this instability initiates and possibly drives the main acceleration. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1420 KW - solar coronal mass ejections KW - stellar coronal mass ejections KW - solar storm Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-519720 SN - 1866-8372 IS - 2 ER - TY - JOUR A1 - Cheng, Xin A1 - Zhang, Jie A1 - Kliem, Bernhard A1 - Török, Tibor A1 - Xing, Chen A1 - Zhou, Zhenjun A1 - Inhester, Bernd A1 - Ding, Mingde T1 - Initiation and early kinematic evolution of solar eruptions JF - The Astrophysical Journal N2 - We investigate the initiation and early evolution of 12 solar eruptions, including six active-region hot channel and six quiescent filament eruptions, which were well observed by the Solar Dynamics Observatory, as well as by the Solar Terrestrial Relations Observatory for the latter. The sample includes one failed eruption and 11 coronal mass ejections, with velocities ranging from 493 to 2140 km s(-1). A detailed analysis of the eruption kinematics yields the following main results. (1) The early evolution of all events consists of a slow-rise phase followed by a main-acceleration phase, the height-time profiles of which differ markedly and can be best fit, respectively, by a linear and an exponential function. This indicates that different physical processes dominate in these phases, which is at variance with models that involve a single process. (2) The kinematic evolution of the eruptions tends to be synchronized with the flare light curve in both phases. The synchronization is often but not always close. A delayed onset of the impulsive flare phase is found in the majority of the filament eruptions (five out of six). This delay and its trend to be larger for slower eruptions favor ideal MHD instability models. (3) The average decay index at the onset heights of the main acceleration is close to the threshold of the torus instability for both groups of events (although, it is based on a tentative coronal field model for the hot channels), suggesting that this instability initiates and possibly drives the main acceleration. KW - solar coronal mass ejections KW - stellar coronal mass ejections KW - solar storm Y1 - 2020 U6 - https://doi.org/10.3847/1538-4357/ab886a SN - 1055-6796 SN - 1476-3540 VL - 894 IS - 2 SP - 1 EP - 20 PB - Cambridge Scientific Publishers CY - Cambridge ER - TY - JOUR A1 - Chigarev, Vladimir A1 - Kazakov, Alexey A1 - Pikovsky, Arkady T1 - Kantorovich-Rubinstein-Wasserstein distance between overlapping attractor and repeller JF - Chaos : an interdisciplinary journal of nonlinear science N2 - We consider several examples of dynamical systems demonstrating overlapping attractor and repeller. These systems are constructed via introducing controllable dissipation to prototypic models with chaotic dynamics (Anosov cat map, Chirikov standard map, and incompressible three-dimensional flow of the ABC-type on a three-torus) and ergodic non-chaotic behavior (skew-shift map). We employ the Kantorovich-Rubinstein-Wasserstein distance to characterize the difference between the attractor and the repeller, in dependence on the dissipation level. Y1 - 2020 U6 - https://doi.org/10.1063/5.0007230 SN - 1054-1500 SN - 1089-7682 VL - 30 IS - 7 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Christ, Simon T1 - Morphological transitions of vesicles exposed to nonuniform spatio-temporal conditions N2 - Giant unilamellar vesicles are an important tool in todays experimental efforts to understand the structure and behaviour of biological cells. Their simple structure allows the isolation of the physical elastic properties of the lipid membrane. A central physical property is the bending energy of the membrane, since the many different shapes of giant vesicles can be obtained by finding the minimum of the bending energy. In the spontaneous curvature model the bending energy is a function of the bending rigidity as well as the mean curvature and an additional parameter called the spontaneous curvature, which describes an internal preference of the lipid-bilayer to bend towards one side or the other. The spontaneous and mean curvature are local properties of the membrane. Additional constraints arise from the conservation of the membrane surface area and the enclosed volume, which are global properties. In this thesis the spontaneous curvature model is used to explain the experimental observation of a periodic shape oscillation of a giant unilamellar vesicle that was filled with a protein complex that periodically binds to and unbinds from the membrane. By assuming that the binding of the proteins to the membrane induces a change in the spontaneous curvature the experimentally observed shapes could successfully be explained. This involves the numerical solution of the differential equations as obtained from the minimization of the bending energy respecting the area and volume constraints, the so called shape equations. Vice versa this approach can be used to estimate the spontaneous curvature from experimentally measurable quantities. The second topic of this thesis is the analysis of concentration gradients in rigid conic membrane compartments. Gradients of an ideal gas due to gravity and gradients generated by the directed stochastic movement of molecular motors along a microtubulus were considered. It was possible to calculate the free energy and the bending energy analytically for the ideal gas. In the case of the non-equilibrium system with molecular motors, the characteristic length of the density profile, the jam-length, and its dependency on the opening angle of the conic compartment have been calculated in the mean-field limit. The mean field results agree qualitatively with stochastic particle simulations. N2 - Die Morphologie beschreibt die Struktur und Form von Organismen. Im Rahmen dieser Arbeit werden insbesondere die verschiedenen Formen von einfachen Lipidmembranen untersucht, die geschlossene Formen in Lösung bilden, die Vesikel. Der Fokus liegt dabei auf Begebenheiten, in denen die es inhomogene Zustände innerhalb oder außerhalb des Vesikels gibt. Das betrifft zum einen die Erklärung der beobachteten Formen in einem Experiment, bei dem im Inneren des Vesikels Proteine plaziert wurden, die sich wiederkehrend an die innere Vesikelmembran heften und wieder ablösen. Dabei Verändert sich die Form des Vesikels von einer symmetrischen erdnussähnlichen Form zu einer asymmetrischen Form mit einem sehr dünnen Hals. Mittels eines theoretischem Modells, dass dem Anheften der Proteine eine Änderung in ihrer bevorzugten Krümmung zuweist, werden Formen berechnet, die den beobachteten Formen gleichen und nur durch das Variieren der bevorzugten Krümmung kann derselbe Formübergang erzielt werden. Außerdem wird die Biegeenergie von Vesikeln, die durch die äußere Umgebung in eine kegelförmige Form gezwungen werden, in Abhängigkeit des Öffnungswinkels des Kegels analytisch berechnet. Es wird weiterhin die freie Energie eines idealen Gases, das durch die Kräfte der Gravitation inhomogen verteilt ist, innerhalb solcher starren kegelförmigen Vesikeln analytisch berechnet. Ein weiteres System, das betrachtet wird, sind molekulare Motoren, die die Fähigkeit besitzen, sich entlang bestimmter Stränge, der Mikrotubuli, gerichtet fortzubewegen und wenn sie sich nicht an einem Mikrotubulus befinden, bewegen sie sich aufgrund der üblichen ungerichteten Kräfte, der Diffusion. Wenn nur ein Mikrotubulus und nur eine Art von Motoren vorhanden ist, entsteht dadurch eine Anhäufung von Teilchen auf der Seite in die die Motoren sich bewegen, ein Konzentrationsgradient. Es wird analytisch berechnet, wie sich dieser Konzentrationsgradient verschiebt, wenn sich der Öffnungswinkel des Kegels ändert und mit Ergebnissen aus Computersimulationen verglichen. T2 - Morphologische Übergänge von Vesikeln unter räumlich oder zeitlich inhomogenen Bedingunge KW - Formgleichungen von Vesikeln KW - Shape equations of vesicles KW - Molekulare Motoren KW - Molecular motors KW - Conic compartments KW - Kegelförmige Geometrien KW - Bending energy KW - Biegeenergie KW - Min-Proteine KW - Min-proteins Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-480788 ER - TY - GEN A1 - Ciemer, Catrin A1 - Rehm, Lars A1 - Kurths, Jürgen A1 - Donner, Reik Volker A1 - Winkelmann, Ricarda A1 - Boers, Niklas T1 - An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1207 KW - complex networks KW - droughts KW - prediction KW - Amazon rainforest Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525863 SN - 1866-8372 IS - 9 ER - TY - JOUR A1 - Ciemer, Catrin A1 - Rehm, Lars A1 - Kurths, Jürgen A1 - Donner, Reik Volker A1 - Winkelmann, Ricarda A1 - Boers, Niklas T1 - An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures JF - Environmental Research Letters N2 - Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months. KW - complex networks KW - droughts KW - prediction KW - Amazon rainforest Y1 - 2019 VL - 15 IS - 9 PB - IOP - Institute of Physics Publishing CY - Bristol ER - TY - JOUR A1 - Crovetto, Andrea A1 - Hempel, Hannes A1 - Rusu, Marin A1 - Choubrac, Leo A1 - Kojda, Sandrino Danny A1 - Habicht, Klaus A1 - Unold, Thomas T1 - Water adsorption enhances electrical conductivity in transparent p-type CuI JF - ACS applied materials & interfaces N2 - CuI has been recently rediscovered as a p-type transparent conductor with a high figure of merit. Even though many metal iodides are hygroscopic, the effect of moisture on the electrical properties of CuI has not been clarified. In this work, we observe a 2-fold increase in the conductivity of CuI after exposure to ambient humidity for 5 h, followed by slight long-term degradation. Simultaneously, the work function of CuI decreases by almost 1 eV, which can explain the large spread in the previously reported work function values. The conductivity increase is partially reversible and is maximized at intermediate humidity levels. On the basis of the large intragrain mobility measured by THz spectroscopy, we suggest that hydration of grain boundaries may be beneficial for the overall hole mobility. KW - transparent conductors KW - CuI KW - copper iodide KW - conductivity KW - humidity KW - p-type KW - work function Y1 - 2020 U6 - https://doi.org/10.1021/acsami.0c11040 SN - 1944-8244 SN - 1944-8252 VL - 12 IS - 43 SP - 48741 EP - 48747 PB - American Chemical Society CY - Washington, DC ER - TY - THES A1 - Dahlke, Sandro T1 - Rapid climate changes in the arctic region of Svalbard T1 - Aktuelle Klimaänderungen in der Svalbard-Region BT - processes, implications and representativeness for the broader Arctic BT - Prozesse, Auswirkungen und Repräsentativität für die Arktis N2 - Over the last decades, the Arctic regions of the earth have warmed at a rate 2–3 times faster than the global average– a phenomenon called Arctic Amplification. A complex, non-linear interplay of physical processes and unique pecularities in the Arctic climate system is responsible for this, but the relative role of individual processes remains to be debated. This thesis focuses on the climate change and related processes on Svalbard, an archipelago in the North Atlantic sector of the Arctic, which is shown to be a "hotspot" for the amplified recent warming during winter. In this highly dynamical region, both oceanic and atmospheric large-scale transports of heat and moisture interfere with spatially inhomogenous surface conditions, and the corresponding energy exchange strongly shapes the atmospheric boundary layer. In the first part, Pan-Svalbard gradients in the surface air temperature (SAT) and sea ice extent (SIE) in the fjords are quantified and characterized. This analysis is based on observational data from meteorological stations, operational sea ice charts, and hydrographic observations from the adjacent ocean, which cover the 1980–2016 period. It is revealed that typical estimates of SIE during late winter range from 40–50% (80–90%) in the western (eastern) parts of Svalbard. However, strong SAT warming during winter of the order of 2–3K per decade dictates excessive ice loss, leaving fjords in the western parts essentially ice-free in recent winters. It is further demostrated that warm water currents on the west coast of Svalbard, as well as meridional winds contribute to regional differences in the SIE evolution. In particular, the proximity to warm water masses of the West Spitsbergen Current can explain 20–37% of SIE variability in fjords on west Svalbard, while meridional winds and associated ice drift may regionally explain 20–50% of SIE variability in the north and northeast. Strong SAT warming has overruled these impacts in recent years, though. In the next part of the analysis, the contribution of large-scale atmospheric circulation changes to the Svalbard temperature development over the last 20 years is investigated. A study employing kinematic air-back trajectories for Ny-Ålesund reveals a shift in the source regions of lower-troposheric air over time for both the winter and the summer season. In winter, air in the recent decade is more often of lower-latitude Atlantic origin, and less frequent of Arctic origin. This affects heat- and moisture advection towards Svalbard, potentially manipulating clouds and longwave downward radiation in that region. A closer investigation indicates that this shift during winter is associated with a strengthened Ural blocking high and Icelandic low, and contributes about 25% to the observed winter warming on Svalbard over the last 20 years. Conversely, circulation changes during summer include a strengthened Greenland blocking high which leads to more frequent cold air advection from the central Arctic towards Svalbard, and less frequent air mass origins in the lower latitudes of the North Atlantic. Hence, circulation changes during winter are shown to have an amplifying effect on the recent warming on Svalbard, while summer circulation changes tend to mask warming. An observational case study using upper air soundings from the AWIPEV research station in Ny-Ålesund during May–June 2017 underlines that such circulation changes during summer are associated with tropospheric anomalies in temperature, humidity and boundary layer height. In the last part of the analysis, the regional representativeness of the above described changes around Svalbard for the broader Arctic is investigated. Therefore, the terms in the diagnostic temperature equation in the Arctic-wide lower troposphere are examined for the Era-Interim atmospheric reanalysis product. Significant positive trends in diabatic heating rates, consistent with latent heat transfer to the atmosphere over regions of increasing ice melt, are found for all seasons over the Barents/Kara Seas, and in individual months in the vicinity of Svalbard. The above introduced warm (cold) advection trends during winter (summer) on Svalbard are successfully reproduced. Regarding winter, they are regionally confined to the Barents Sea and Fram Strait, between 70°–80°N, resembling a unique feature in the whole Arctic. Summer cold advection trends are confined to the area between eastern Greenland and Franz Josef Land, enclosing Svalbard. N2 - Die Arktis hast sich über die letzten Jahrzehnte etwa 2–3 mal so schnell erwärmt wie die globale Mitteltemperatur der Erde, wofür der Begriff Arktische Verstärkung geprägt wurde. Eine komplexe Kaskade nichtlinear miteinander interagierender Prozesse und lokaler Bedingungen ist für das Auftreten dieses Phänomens verantwortlich, jedoch bleibt ein wissenschaftlicher Konsens zur Quantifizierung einzelner beteiligter Prozesse noch aus. Diese Arbeit befasst sich mit den Klimaänderungen und assoziierten Prozessen in der Svalbard-Region, einem arktischen Archipel im Nordatlantik. Svalbard kann als Brennpunkt der arktischen Veränderungen bezeichnet werden, vor allem während des Winters. In dieser ausgesprochen dynamischen Region interagieren die Energieflüsse durch großskalige atmosphärische und ozeanische Wärme- und Feuchtetransporte mit der heteorogenen Oberfläche, die sich aus Eis-, Wasser-, oder Landflächen zusammensetzt. Die daraus resultierenden horizontalen und vertikalen Energieflüsse stehen in engem Zusammenhang mit der Beschaffenheit der atmosphärischen Grenzschicht. Im ersten Teil dieser Arbeit werden laterale Unterschiede in der Oberflächentemperatur (SAT), sowie der Meereisbedeckung (SIE) in den Fjorden und Sunden des Archipels quantifiziert und klassifiziert. Dies geschieht auf der Grundlage von meteorologischen Stationsmessdaten und operationellen Eisbedeckungskarten der Jahe 1980–2016. Es zeigt sich, dass prozentuale Eisbedeckungen im Osten des Studiengebietes typischerweise 80–90% im Winter erreichen, während diese Werte in Fjorden der Westküste mit 40–50% deutlich niedriger liegen. Allerdings bedingt eine starke, winterliche SAT Erwärmung von 2–3K pro Jahrzehnt signifikante SIE Abwärtstrends, sodass die Fjorde im Westen von Svalbard in den jüngeren Wintern üblicherweise eisfrei waren. Im Weiteren wird gezeigt dass die warmen Ozeanströmungen nahe der Westküste, sowie spezielle Windkonstellationen, einen signifikanten regionalen Einfluss auf die langzeitliche Entwicklung der Meereisbedeckung ausüben. So kann Variabilität in der Temperatur des Westspitzbergenstroms etwa 20–37% der zwischenjährlichen SIE Variabilität in den Fjorden der Westküste erklären. Die meridionale Atmosphärenströmung nordwestlich von Spitzbergen, die hochkorelliert mit Eisdrift ist, kann andererseits –regional abhängig– etwa 20–50% der SIE-Variablität in den nördlichen und nordöstlichen Fjorden erklären. Durch den starken temperaturbedingten Eisrückgang in der gesamten Region sind diese Einflüsse zuletzt jedoch stark abgeschwächt. Im Folgenden wird der Beitrag von Zirkulationsänderungen zur Temperaturentwicklung Svalbards während der letzten 20 Jahre untersucht. Die Analyse basiert auf den Quellregionen troposphärischer Luftmassen, die sich aus kinematischen FLEXTRA-Rückwärtstrajektorien ergeben. Für den Winter zeigt sich, dass sich diese zuletzt immer häufiger in sub-arktische Gebiete über dem Nordatlantik verlagert hatten, und seltener in der hohen Arktis lagen. Dies moduliert Warmluft-, und Feuchtetransporte in Richtung Spitzbergen, und beeinflusst potentiell Wolkencharakteristiken und assoziierte Strahlungsprozesse. Nähere Untersuchen zeigen dass ein zuletzt stärker ausgeprägtes Uralhoch und Islandtief dafür verantwortlich sind, und dass dies einen Beitrag von etwa 25% zur jüngsten Wintererwärmung auf Spitzbergen hat. Sommertrajektorien offenbaren eine gegensätzliche Entwicklung, mit häufigerer Anströmung aus der Zentralarktis, welche mit Kaltluftadvektion einhergeht, auf Kosten von seltenerer Anströmung aus dem Süden. Dies liegt in einem während der letzten 10 Jahre stark ausgeprägten Grönlandhoch begründet. Eine Fallstudie anhand von Radiosondendaten vom Frühsommer 2017 untermauert die Ergebnisse und zeigt darüber hinaus, dass derartige Zirkulationsänderungen mit ausgeprägten Anomalien von troposphärischen Temperaturen,Feuchtigkeit, und der Grenzschichthöhe in Ny-Ålesund einher geht. Interessanterweise tragen Zirkulationsänderungen im Winter also verstärkend zur Erwärmung auf Svalbard bei, während jene im Sommer einer stärkeren Erwärmung entgegenwirken. In einem letzten Analyseschritt wird die regionale Repräsentativität der Region für die weitere Arktis erörtert. Die Analyse von Era-Interim Reanalysedaten untermauert hierbei zunächst die advektiven Temperaturänderungen in Sommer und Winter in der Region um Svalbard. Der Trend zu verstärkt positiver winterlicher Temperaturadvektion ist einzigartig in der Arktis und beschränkt sich auf die Regionen zwischen Barentssee, Spitzbergen und der nördlichen Framstraße. Die sommerliche erhöhte Kaltluftadvektion findet sich in einem weiten Gebiet zwischen der Ostküste Grönlands und Franz-Josef-Land, welches Svalbard einschließt. Ein diabatischer Erwärmungstrend, der mit aufwärts gerichteten latenten Energieflüssen und Eisrückgang konsistent ist, findet sich in allen Jahreszeiten über der Barents/Karasee wieder, und erstreckt sich in einzelnen Monaten bis nach Svalbard. KW - arctic KW - climate KW - Svalbard KW - meteorology KW - climatology KW - atmosphere KW - Arktis KW - Klima KW - Svalbard KW - Meteorologie KW - Klimatologie KW - Atmosphäre Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-445542 ER -