TY - JOUR A1 - Drozdov, Alexander A1 - Allison, Hayley J. A1 - Shprits, Yuri Y. A1 - Usanova, Maria E. A1 - Saikin, Anthony A1 - Wang, Dedong T1 - Depletions of Multi-MeV Electrons and their association to Minima in Phase Space Density JF - Geophysical research letters N2 - Fast-localized electron loss, resulting from interactions with electromagnetic ion cyclotron (EMIC) waves, can produce deepening minima in phase space density (PSD) radial profiles. Here, we perform a statistical analysis of local PSD minima to quantify how readily these are associated with radiation belt depletions. The statistics of PSD minima observed over a year are compared to the Versatile Electron Radiation Belts (VERB) simulations, both including and excluding EMIC waves. The observed minima distribution can only be achieved in the simulation including EMIC waves, indicating their importance in the dynamics of the radiation belts. By analyzing electron flux depletions in conjunction with the observed PSD minima, we show that, in the heart of the outer radiation belt (L* < 5), on average, 53% of multi-MeV electron depletions are associated with PSD minima, demonstrating that fast localized loss by interactions with EMIC waves are a common and crucial process for ultra-relativistic electron populations. KW - radiation belts KW - EMIC KW - VERB KW - PSD Y1 - 2022 U6 - https://doi.org/10.1029/2021GL097620 SN - 0094-8276 SN - 1944-8007 VL - 49 IS - 8 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Grebenkov, Denis S. A1 - Metzler, Ralf A1 - Oshanin, Gleb T1 - Search efficiency in the Adam-Delbruck reduction-of-dimensionality scenario versus direct diffusive search JF - New journal of physics : the open-access journal for physics N2 - The time instant-the first-passage time (FPT)-when a diffusive particle (e.g., a ligand such as oxygen or a signalling protein) for the first time reaches an immobile target located on the surface of a bounded three-dimensional domain (e.g., a hemoglobin molecule or the cellular nucleus) is a decisive characteristic time-scale in diverse biophysical and biochemical processes, as well as in intermediate stages of various inter- and intra-cellular signal transduction pathways. Adam and Delbruck put forth the reduction-of-dimensionality concept, according to which a ligand first binds non-specifically to any point of the surface on which the target is placed and then diffuses along this surface until it locates the target. In this work, we analyse the efficiency of such a scenario and confront it with the efficiency of a direct search process, in which the target is approached directly from the bulk and not aided by surface diffusion. We consider two situations: (i) a single ligand is launched from a fixed or a random position and searches for the target, and (ii) the case of 'amplified' signals when N ligands start either from the same point or from random positions, and the search terminates when the fastest of them arrives to the target. For such settings, we go beyond the conventional analyses, which compare only the mean values of the corresponding FPTs. Instead, we calculate the full probability density function of FPTs for both scenarios and study its integral characteristic-the 'survival' probability of a target up to time t. On this basis, we examine how the efficiencies of both scenarios are controlled by a variety of parameters and single out realistic conditions in which the reduction-of-dimensionality scenario outperforms the direct search. KW - first-passage times KW - Adam-Delbruck scenario KW - dimensional reduction KW - bulk KW - and surface diffusion Y1 - 2022 U6 - https://doi.org/10.1088/1367-2630/ac8824 SN - 1367-2630 VL - 24 IS - 8 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Wang, Wei A1 - Metzler, Ralf A1 - Sokolov, Igor M. T1 - Inertia triggers nonergodicity of fractional Brownian motion JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - How related are the ergodic properties of the over- and underdamped Langevin equations driven by fractional Gaussian noise? We here find that for massive particles performing fractional Brownian motion (FBM) inertial effects not only destroy the stylized fact of the equivalence of the ensemble-averaged mean-squared displacement (MSD) to the time-averaged MSD (TAMSD) of overdamped or massless FBM, but also dramatically alter the values of the ergodicity-breaking parameter (EB). Our theoretical results for the behavior of EB for underdamped or massive FBM for varying particle mass m, Hurst exponent H, and trace length T are in excellent agreement with the findings of stochastic computer simulations. The current results can be of interest for the experimental community employing various single-particle-tracking techniques and aiming at assessing the degree of nonergodicity for the recorded time series (studying, e.g., the behavior of EB versus lag time). To infer FBM as a realizable model of anomalous diffusion for a set single-particle-tracking data when massive particles are being tracked, the EBs from the data should be compared to EBs of massive (rather than massless) FBM. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevE.104.024115 SN - 2470-0045 SN - 2470-0053 VL - 104 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Klett, Kolja A1 - Cherstvy, Andrey G. A1 - Shin, Jaeoh A1 - Sokolov, Igor M. A1 - Metzler, Ralf T1 - Non-Gaussian, transiently anomalous, and ergodic self-diffusion of flexible dumbbells in crowded two-dimensional environments BT - coupled translational and rotational motions JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We employ Langevin-dynamics simulations to unveil non-Brownian and non-Gaussian center-of-mass self-diffusion of massive flexible dumbbell-shaped particles in crowded two-dimensional solutions. We study the intradumbbell dynamics of the relative motion of the two constituent elastically coupled disks. Our main focus is on effects of the crowding fraction phi and of the particle structure on the diffusion characteristics. We evaluate the time-averaged mean-squared displacement (TAMSD), the displacement probability-density function (PDF), and the displacement autocorrelation function (ACF) of the dimers. For the TAMSD at highly crowded conditions of dumbbells, e.g., we observe a transition from the short-time ballistic behavior, via an intermediate subdiffusive regime, to long-time Brownian-like spreading dynamics. The crowded system of dimers exhibits two distinct diffusion regimes distinguished by the scaling exponent of the TAMSD, the dependence of the diffusivity on phi, and the features of the displacement-ACF. We attribute these regimes to a crowding-induced transition from viscous to viscoelastic diffusion upon growing phi. We also analyze the relative motion in the dimers, finding that larger phi suppress their vibrations and yield strongly non-Gaussian PDFs of rotational displacements. For the diffusion coefficients D(phi) of translational and rotational motion of the dumbbells an exponential decay with phi for weak and a power-law variation D(phi) proportional to (phi - phi(star))(2.4) for strong crowding is found. A comparison of simulation results with theoretical predictions for D(phi) is discussed and some relevant experimental systems are overviewed. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevE.104.064603 SN - 2470-0045 SN - 2470-0053 VL - 104 IS - 6 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Bolotov, Maxim I. A1 - Smirnov, Lev A. A1 - Bubnova, E. S. A1 - Osipov, Grigory V. A1 - Pikovskij, Arkadij T1 - Spatiotemporal regimes in the Kuramoto-Battogtokh system of nonidentical oscillators JF - Journal of experimental and theoretical physics N2 - We consider the spatiotemporal states of an ensemble of nonlocally coupled nonidentical phase oscillators, which correspond to different regimes of the long-term evolution of such a system. We have obtained homogeneous, twisted, and nonhomogeneous stationary solutions to the Ott-Antonsen equations corresponding to key variants of the realized collective rotational motion of elements of the medium in question with nonzero mesoscopic characteristics determining the degree of coherence of the dynamics of neighboring particles. We have described the procedures of the search for the class of nonhomogeneous solutions as stationary points of the auxiliary point map and of determining the stability based on analysis of the eigenvalue spectrum of the composite operator. Static and breather cluster regimes have been demonstrated and described, as well as the regimes with an irregular behavior of averaged complex fields including, in particular, the local order parameter. Y1 - 2021 U6 - https://doi.org/10.1134/S1063776121010106 SN - 1063-7761 SN - 1090-6509 VL - 132 IS - 1 SP - 127 EP - 147 PB - Springer CY - Heidelberg [u.a.] ER - TY - JOUR A1 - Vilk, Ohad A1 - Aghion, Erez A1 - Nathan, Ran A1 - Toledo, Sivan A1 - Metzler, Ralf A1 - Assaf, Michael T1 - Classification of anomalous diffusion in animal movement data using power spectral analysis JF - Journal of physics : A, Mathematical and theoretical N2 - The field of movement ecology has seen a rapid increase in high-resolution data in recent years, leading to the development of numerous statistical and numerical methods to analyse relocation trajectories. Data are often collected at the level of the individual and for long periods that may encompass a range of behaviours. Here, we use the power spectral density (PSD) to characterise the random movement patterns of a black-winged kite (Elanus caeruleus) and a white stork (Ciconia ciconia). The tracks are first segmented and clustered into different behaviours (movement modes), and for each mode we measure the PSD and the ageing properties of the process. For the foraging kite we find 1/f noise, previously reported in ecological systems mainly in the context of population dynamics, but not for movement data. We further suggest plausible models for each of the behavioural modes by comparing both the measured PSD exponents and the distribution of the single-trajectory PSD to known theoretical results and simulations. KW - diffusion KW - anomalous diffusion KW - power spectral analysis KW - ecological KW - movement data Y1 - 2022 U6 - https://doi.org/10.1088/1751-8121/ac7e8f SN - 1751-8113 SN - 1751-8121 VL - 55 IS - 33 PB - IOP Publishing CY - Bristol ER - TY - JOUR A1 - Sposini, Vittoria A1 - Chechkin, Aleksei A1 - Sokolov, Igor M. A1 - Roldan-Vargas, Sandalo T1 - Detecting temporal correlations in hopping dynamics in Lennard-Jones liquids JF - Journal of physics : A, Mathematical and theoretical N2 - Lennard-Jones mixtures represent one of the popular systems for the study of glass-forming liquids. Spatio/temporal heterogeneity and rare (activated) events are at the heart of the slow dynamics typical of these systems. Such slow dynamics is characterised by the development of a plateau in the mean-squared displacement (MSD) at intermediate times, accompanied by a non-Gaussianity in the displacement distribution identified by exponential tails. As pointed out by some recent works, the non-Gaussianity persists at times beyond the MSD plateau, leading to a Brownian yet non-Gaussian regime and thus highlighting once again the relevance of rare events in such systems. Single-particle motion of glass-forming liquids is usually interpreted as an alternation of rattling within the local cage and cage-escape motion and therefore can be described as a sequence of waiting times and jumps. In this work, by using a simple yet robust algorithm, we extract jumps and waiting times from single-particle trajectories obtained via molecular dynamics simulations. We investigate the presence of correlations between waiting times and find negative correlations, which becomes more and more pronounced when lowering the temperature. KW - glassy systems KW - hopping dynamics KW - jump detection KW - rare events Y1 - 2022 U6 - https://doi.org/10.1088/1751-8121/ac7e0a SN - 1751-8113 SN - 1751-8121 VL - 55 IS - 32 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Krämer, Hauke Kai A1 - Gelbrecht, Maximilian A1 - Pavithran, Induja A1 - Sujith, Ravindran A1 - Marwan, Norbert T1 - Optimal state space reconstruction via Monte Carlo decision tree search JF - Nonlinear Dynamics N2 - A novel idea for an optimal time delay state space reconstruction from uni- and multivariate time series is presented. The entire embedding process is considered as a game, in which each move corresponds to an embedding cycle and is subject to an evaluation through an objective function. This way the embedding procedure can be modeled as a tree, in which each leaf holds a specific value of the objective function. By using a Monte Carlo ansatz, the proposed algorithm populates the tree with many leafs by computing different possible embedding paths and the final embedding is chosen as that particular path, which ends at the leaf with the lowest achieved value of the objective function. The method aims to prevent getting stuck in a local minimum of the objective function and can be used in a modular way, enabling practitioners to choose a statistic for possible delays in each embedding cycle as well as a suitable objective function themselves. The proposed method guarantees the optimization of the chosen objective function over the parameter space of the delay embedding as long as the tree is sampled sufficiently. As a proof of concept, we demonstrate the superiority of the proposed method over the classical time delay embedding methods using a variety of application examples. We compare recurrence plot-based statistics inferred from reconstructions of a Lorenz-96 system and highlight an improved forecast accuracy for map-like model data as well as for palaeoclimate isotope time series. Finally, we utilize state space reconstruction for the detection of causality and its strength between observables of a gas turbine type thermoacoustic combustor. KW - State space reconstruction KW - Embedding KW - Optimization KW - Time series analysis KW - Causality KW - Prediction KW - Recurrence analysis Y1 - 2022 U6 - https://doi.org/10.1007/s11071-022-07280-2 SN - 0924-090X SN - 1573-269X VL - 108 IS - 2 SP - 1525 EP - 1545 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Yuan, Jun A1 - Zhang, Chujun A1 - Qiu, Beibei A1 - Liu, Wei A1 - So, Shu Kong A1 - Mainville, Mathieu A1 - Leclerc, Mario A1 - Shoaee, Safa A1 - Neher, Dieter A1 - Zou, Yingping T1 - Effects of energetic disorder in bulk heterojunction organic solar cells JF - Energy & environmental science N2 - Organic solar cells (OSCs) have progressed rapidly in recent years through the development of novel organic photoactive materials, especially non-fullerene acceptors (NFAs). Consequently, OSCs based on state-of-the-art NFAs have reached significant milestones, such as similar to 19% power conversion efficiencies (PCEs) and small energy losses (less than 0.5 eV). Despite these significant advances, understanding of the interplay between molecular structure and optoelectronic properties lags significantly behind. For example, despite the theoretical framework for describing the energetic disorder being well developed for the case of inorganic semiconductors, the question of the applicability of classical semiconductor theories in analyzing organic semiconductors is still under debate. A general observation in the inorganic field is that inorganic photovoltaic materials possessing a polycrystalline microstructure exhibit suppressed disorder properties and better charge carrier transport compared to their amorphous analogs. Accordingly, this principle extends to the organic semiconductor field as many organic photovoltaic materials are synthesized to pursue polycrystalline-like features. Yet, there appears to be sporadic examples that exhibit an opposite trend. However, full studies decoupling energetic disorder from aggregation effects have largely been left out. Hence, the potential role of the energetic disorder in OSCs has received little attention. Interestingly, recently reported state-of-the-art NFA-based devices could achieve a small energetic disorder and high PCE at the same time; and interest in this investigation related to the disorder properties in OSCs was revived. In this contribution, progress in terms of the correlation between molecular design and energetic disorder is reviewed together with their effects on the optoelectronic mechanism and photovoltaic performance. Finally, the specific challenges and possible solutions in reducing the energetic disorder of OSCs from the viewpoint of materials and devices are proposed. Y1 - 2022 U6 - https://doi.org/10.1039/d2ee00271j SN - 1754-5692 SN - 1754-5706 VL - 15 IS - 7 SP - 2806 EP - 2818 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kroh, Daniel A1 - Eller, Fabian A1 - Schötz, Konstantin A1 - Wedler, Stefan A1 - Perdigón-Toro, Lorena A1 - Freychet, Guillaume A1 - Wei, Qingya A1 - Dörr, Maximilian A1 - Jones, David A1 - Zou, Yingping A1 - Herzig, Eva M. A1 - Neher, Dieter A1 - Köhler, Anna T1 - Identifying the signatures of intermolecular interactions in blends of PM6 with Y6 and N4 using absorption spectroscopy JF - Advanced functional materials N2 - In organic solar cells, the resulting device efficiency depends strongly on the local morphology and intermolecular interactions of the blend film. Optical spectroscopy was used to identify the spectral signatures of interacting chromophores in blend films of the donor polymer PM6 with two state-of-the-art nonfullerene acceptors, Y6 and N4, which differ merely in the branching point of the side chain. From temperature-dependent absorption and luminescence spectroscopy in solution, it is inferred that both acceptor materials form two types of aggregates that differ in their interaction energy. Y6 forms an aggregate with a predominant J-type character in solution, while for N4 molecules the interaction is predominantly in a H-like manner in solution and freshly spin-cast film, yet the molecules reorient with respect to each other with time or thermal annealing to adopt a more J-type interaction. The different aggregation behavior of the acceptor materials is also reflected in the blend films and accounts for the different solar cell efficiencies reported with the two blends. KW - charge-transfer states KW - Frank-Condon analysis KW - morphology KW - organic solar cells Y1 - 2022 U6 - https://doi.org/10.1002/adfm.202205711 SN - 1616-301X SN - 1616-3028 VL - 32 IS - 44 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Grebenkov, Denis S. A1 - Kumar, Aanjaneya T1 - First-passage times of multiple diffusing particles with reversible target-binding kinetics JF - Journal of physics : A, Mathematical and theoretical N2 - We investigate a class of diffusion-controlled reactions that are initiated at the time instance when a prescribed number K among N particles independently diffusing in a solvent are simultaneously bound to a target region. In the irreversible target-binding setting, the particles that bind to the target stay there forever, and the reaction time is the Kth fastest first-passage time to the target, whose distribution is well-known. In turn, reversible binding, which is common for most applications, renders theoretical analysis much more challenging and drastically changes the distribution of reaction times. We develop a renewal-based approach to derive an approximate solution for the probability density of the reaction time. This approximation turns out to be remarkably accurate for a broad range of parameters. We also analyze the dependence of the mean reaction time or, equivalently, the inverse reaction rate, on the main parameters such as K, N, and binding/unbinding constants. Some biophysical applications and further perspectives are briefly discussed. KW - first-passage time KW - diffusion-controlled reactions KW - reversible binding KW - extreme statistics Y1 - 2022 U6 - https://doi.org/10.1088/1751-8121/ac7e91 SN - 1751-8113 SN - 1751-8121 VL - 55 IS - 32 PB - IOP Publ. CY - Bristol ER - TY - JOUR A1 - Werner, Klaus A1 - Reindl, Nicole A1 - Dorsch, Matti A1 - Geier, Stephan A1 - Munari, Ulisse A1 - Raddi, Roberto T1 - Non-local thermodynamic equilibrium spectral analysis of five hot, hydrogen-deficient pre-white dwarfs JF - Astronomy and Astrophysics N2 - Hot, compact, hydrogen-deficient pre-white dwarfs (pre-WDs) with effective temperatures of Teff > 70 000 K and a surface gravity of 5.0 < logg < 7.0 are rather rare objects despite recent and ongoing surveys. It is believed that they are the outcome of either single star evolution (late helium-shell flash or late helium-core flash) or binary star evolution (double WD merger). Their study is interesting because the surface elemental abundances reflect the physics of thermonuclear flashes and merger events. Spectroscopically they are divided in three different classes, namely PG1159, O(He), or He-sdO. We present a spectroscopic analysis of five such stars that turned out to have atmospheric parameters in the range Teff = 70 000-80 000 K and logg = 5.2-6.3. The three investigated He-sdOs have a relatively high hydrogen mass fraction (10%) that is unexplained by both single (He core flash) and binary evolution (He-WD merger) scenarios. The O(He) star JL 9 is probably a binary helium-WD merger, but its hydrogen content (6%) is also at odds with merger models. We found that RL 104 is the 'coolest' (Teff = 80 000 K) member of the PG1159 class in a pre-WD stage. Its optical spectrum is remarkable because it exhibits C※ IV lines involving Rydberg states with principal quantum numbers up to n = 22. Its rather low mass (0.48-0.02+0.03 M·) is difficult to reconcile with the common evolutionary scenario for PG1159 stars due to it being the outcome of a (very) late He-shell flash. The same mass-problem faces a merger model of a close He-sdO plus CO WD binary that predicts PG1159-like abundances. Perhaps RL 104 originates from a very late He-shell flash in a CO/He WD formed by a merger of two low-mass He-WDs. KW - stars: atmospheres KW - stars: abundances KW - stars: evolution KW - subdwarfs KW - white dwarfs Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202142397 SN - 0004-6361 SN - 1432-0746 VL - 658 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Smirnov, Lev A. A1 - Bolotov, Maxim I. A1 - Osipov, Grigorij V. A1 - Pikovskij, Arkadij T1 - Disorder fosters chimera in an array of motile particles JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We consider an array of nonlocally coupled oscillators on a ring, which for equally spaced units possesses a Kuramoto-Battogtokh chimera regime and a synchronous state. We demonstrate that disorder in oscillators positions leads to a transition from the synchronous to the chimera state. For a static (quenched) disorder we find that the probability of synchrony survival depends on the number of particles, from nearly zero at small populations to one in the thermodynamic limit. Furthermore, we demonstrate how the synchrony gets destroyed for randomly (ballistically or diffusively) moving oscillators. We show that, depending on the number of oscillators, there are different scalings of the transition time with this number and the velocity of the units. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevE.104.034205 SN - 2470-0045 SN - 2470-0053 VL - 104 IS - 3 PB - American Physical Society CY - Melville, NY ER - TY - JOUR A1 - Shayduk, Roman A1 - Hallmann, Jörg A1 - Rodriguez-Fernandez, Angel A1 - Scholz, Markus A1 - Lu, Wei A1 - Bösenberg, Ulrike A1 - Möller, Johannes A1 - Zozulya, Alexey A1 - Jiang, Man A1 - Wegner, Ulrike A1 - Secareanu, Radu-Costin A1 - Palmer, Guido A1 - Emons, Moritz A1 - Lederer, Max A1 - Volkov, Sergey A1 - Lindfors-Vrejoiu, Ionela A1 - Schick, Daniel A1 - Herzog, Marc A1 - Bargheer, Matias A1 - Madsen, Anders T1 - Femtosecond x-ray diffraction study of multi-THz coherent phonons in SrTiO3 JF - Applied physics letters N2 - We report generation of ultra-broadband longitudinal acoustic coherent phonon wavepackets in SrTiO3 (STO) with frequency components extending throughout the first Brillouin zone. The wavepackets are efficiently generated in STO using femtosecond infrared laser excitation of an atomically flat 1.6 nm-thick epitaxial SrRuO3 film. We use femtosecond x-ray diffraction at the European X-Ray Free Electron Laser Facility to study the dispersion and damping of phonon wavepackets. The experimentally determined damping constants for multi-THz frequency phonons compare favorably to the extrapolation of a simple ultrasound damping model over several orders of magnitude. Y1 - 2022 U6 - https://doi.org/10.1063/5.0083256 SN - 0003-6951 SN - 1077-3118 VL - 120 IS - 20 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Singh, Rishu Kumar A1 - Górska, Katarzyna A1 - Sandev, Trifce T1 - General approach to stochastic resetting JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We address the effect of stochastic resetting on diffusion and subdiffusion process. For diffusion we find that mean square displacement relaxes to a constant only when the distribution of reset times possess finite mean and variance. In this case, the leading order contribution to the probability density function (PDF) of a Gaussian propagator under resetting exhibits a cusp independent of the specific details of the reset time distribution. For subdiffusion we derive the PDF in Laplace space for arbitrary resetting protocol. Resetting at constant rate allows evaluation of the PDF in terms of H function. We analyze the steady state and derive the rate function governing the relaxation behavior. For a subdiffusive process the steady state could exist even if the distribution of reset times possesses only finite mean. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevE.105.064133 SN - 2470-0045 SN - 2470-0053 VL - 105 IS - 6 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Padash, Amin A1 - Sandev, Trifce A1 - Kantz, Holger A1 - Metzler, Ralf A1 - Chechkin, Aleksei T1 - Asymmetric Levy flights are more efficient in random search JF - Fractal and fractional N2 - We study the first-arrival (first-hitting) dynamics and efficiency of a one-dimensional random search model performing asymmetric Levy flights by leveraging the Fokker-Planck equation with a delta-sink and an asymmetric space-fractional derivative operator with stable index alpha and asymmetry (skewness) parameter beta. We find exact analytical results for the probability density of first-arrival times and the search efficiency, and we analyse their behaviour within the limits of short and long times. We find that when the starting point of the searcher is to the right of the target, random search by Brownian motion is more efficient than Levy flights with beta <= 0 (with a rightward bias) for short initial distances, while for beta>0 (with a leftward bias) Levy flights with alpha -> 1 are more efficient. When increasing the initial distance of the searcher to the target, Levy flight search (except for alpha=1 with beta=0) is more efficient than the Brownian search. Moreover, the asymmetry in jumps leads to essentially higher efficiency of the Levy search compared to symmetric Levy flights at both short and long distances, and the effect is more pronounced for stable indices alpha close to unity. KW - asymmetric Levy flights KW - first-arrival density KW - search efficiency Y1 - 2022 U6 - https://doi.org/10.3390/fractalfract6050260 SN - 2504-3110 VL - 6 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Gerlach, Marius A1 - Preitschopf, Tobias A1 - Karaev, Emil A1 - Quitian-Lara, Heidy Mayerly A1 - Mayer, Dennis A1 - Bozek, John A1 - Fischer, Ingo A1 - Fink, Reinhold F. T1 - Auger electron spectroscopy of fulminic acid, HCNO BT - an experimental and theoretical study JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - HCNO is a molecule of considerable astrochemical interest as a precursor to prebiotic molecules. It is synthesized by preparative pyrolysis and is unstable at room temperature. Here, we investigate its spectroscopy in the soft X-ray regime at the C 1s, N 1s and O 1s edges. All 1s ionization energies are reported and X-ray absorption spectra reveal the transitions from the 1s to the pi* state. Resonant and normal Auger electron spectra for the decay of the core hole states are recorded in a hemispherical analyzer. An assignment of the experimental spectra is provided with the aid of theoretical counterparts. The latter are using a valence configuration interaction representation of the intermediate and final state energies and wavefunctions, the one-center approximation for transition rates and band shapes according to the moment theory. The computed spectra are in very good agreement with the experimental data and most of the relevant bands are assigned. Additionally, we present a simple approach to estimate relative Auger transition rates on the basis of a minimal basis representation of the molecular orbitals. We demonstrate that this provides a qualitatively good and reliable estimate for several signals in the normal and resonant Auger electron spectra which have significantly different intensities in the decay of the three core holes. Y1 - 2022 U6 - https://doi.org/10.1039/d2cp02104h SN - 1463-9076 SN - 1463-9084 VL - 24 IS - 25 SP - 15217 EP - 15229 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Fritsch, Tobias A1 - Kurpiers, Jona A1 - Roland, Steffen A1 - Tokmoldin, Nurlan A1 - Shoaee, Safa A1 - Ferron, Thomas A1 - Collins, Brian A. A1 - Janietz, Silvia A1 - Vandewal, Koen A1 - Neher, Dieter T1 - On the interplay between CT and singlet exciton emission in organic solar cells with small driving force and its impact on voltage loss JF - Advanced energy materials N2 - The interplay between free charge carriers, charge transfer (CT) states and singlet excitons (S-1) determines the recombination pathway and the resulting open circuit voltage (V-OC) of organic solar cells. By combining a well-aggregated low bandgap polymer with different blend ratios of the fullerenes PCBM and ICBA, the energy of the CT state (E-CT) is varied by 130 meV while leaving the S-1 energy of the polymer (ES1\[{E_{{{\rm{S}}_1}}}\]) unaffected. It is found that the polymer exciton dominates the radiative properties of the blend when ECT\[{E_{{\rm{CT}}}}\] approaches ES1\[{E_{{{\rm{S}}_1}}}\], while the V-OC remains limited by the non-radiative decay of the CT state. It is concluded that an increasing strength of the exciton in the optical spectra of organic solar cells will generally decrease the non-radiative voltage loss because it lowers the radiative V-OC limit (V-OC,V-rad), but not because it is more emissive. The analysis further suggests that electronic coupling between the CT state and the S-1 will not improve the V-OC, but rather reduce the V-OC,V-rad. It is anticipated that only at very low CT state absorption combined with a fairly high CT radiative efficiency the solar cell benefit from the radiative properties of the singlet excitons. KW - external quantum efficiency KW - organic photovoltaics KW - ternary blends KW - voltage losses Y1 - 2022 U6 - https://doi.org/10.1002/aenm.202200641 SN - 1614-6832 SN - 1614-6840 VL - 12 IS - 31 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ujevic, Maximiliano A1 - Rashti, Alireza A1 - Gieg, Henrique Leonhard A1 - Tichy, Wolfgang A1 - Dietrich, Tim T1 - High-accuracy high-mass-ratio simulations for binary neutron stars and their comparison to existing waveform models JF - Physical review : D, Particles, fields, gravitation, and cosmology N2 - The subsequent observing runs of the advanced gravitational-wave detector network will likely provide us with various gravitational-wave observations of binary neutron star systems. For an accurate interpretation of these detections, we need reliable gravitational-wave models. To test and to point out how existing models could be improved, we perform a set of high-resolution numerical relativity simulations for four different physical setups with mass ratios q = 1.25, 1.50, 1.75, 2.00, and total gravitational mass M = 2.7 M???. Each configuration is simulated with five different resolutions to allow a proper error assessment. Overall, we find approximately second-order converging results for the dominant (2,2) mode, but also the subdominant (2,1), (3,3), and (4,4) modes, while generally, the convergence order reduces slightly for an increasing mass ratio. Our simulations allow us to validate waveform models, where we find generally good agreement between state-of-the-art models and our data, and to prove that scaling relations for higher modes currently employed for binary black hole waveform modeling also apply for the tidal contribution. Finally, we also test if the current NRTidal model used to describe tidal effects is a valid description for high-mass-ratio systems. We hope that our simulation results can be used to further improve and test waveform models in preparation for the next observing runs. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevD.106.023029 SN - 2470-0010 SN - 2470-0029 VL - 106 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Büchner, Robby A1 - da Cruz, Vinicius Vaz A1 - Grover, Nitika A1 - Charisiadis, Asterios A1 - Fondell, Mattis A1 - Haverkamp, Robert A1 - Senge, Mathias O. A1 - Föhlisch, Alexander T1 - Fundamental electronic changes upon intersystem crossing in large aromatic photosensitizers: free base 5,10,15,20-tetrakis(4-carboxylatophenyl)porphyrin JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Free base 5,10,15,20-tetrakis(4-carboxylatophenyl)porphyrin stands for the class of powerful porphyrin photosensitizers for singlet oxygen generation and light-harvesting. The atomic level selectivity of dynamic UV pump - N K-edge probe X-ray absorption spectroscopy in combination with time-dependent density functional theory (TD-DFT) gives direct access to the crucial excited molecular states within the unusual relaxation pathway. The efficient intersystem crossing, that is El-Sayed forbidden and not facilitated by a heavy atom is confirmed to be the result of the long singlet excited state lifetime (Q(x) 4.9 ns) and thermal effects. Overall, the interplay of stabilization by conservation of angular momenta and vibronic relaxation drive the de-excitation in these chromophores. Y1 - 2022 U6 - https://doi.org/10.1039/d1cp05420a SN - 1463-9076 SN - 1463-9084 VL - 24 IS - 12 SP - 7505 EP - 7511 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Dorsch, Matti A1 - Jeffery, C. Simon A1 - Irrgang, Andreas A1 - Woolf, Vincent A1 - Heber, Ulrich T1 - EC 22536-5304 BT - a lead-rich and metal-poor long-period binary JF - Astronomy and astrophysics : an international weekly journal N2 - Helium-burning hot subdwarf stars of spectral types O and B (sdO/B) are thought to be produced through various types of binary interactions. The helium-rich hot subdwarf star EC 22536-5304 was recently found to be extremely enriched in lead. Here, we show that EC 22536-5304 is a binary star with a metal-poor subdwarf F-type (sdF) companion. We performed a detailed analysis of high-resolution SALT/HRS and VLT/UVES spectra, deriving metal abundances for the hot subdwarf, as well as atmospheric parameters for both components. Because we consider the contribution of the sdF star, the derived lead abundance for the sdOB, + 6.3 +/- 0.3 dex relative to solar, is even higher than previously thought. We derive T-eff = 6210 +/- 70 K, log g = 4.64 +/- 0.10, [FE/H] = - 1.95 +/- 0.04, and [alpha/Fe] = + 0.40 +/- 0.04 for the sdF component. Radial velocity variations, although poorly sampled at present, indicate that the binary system has a long orbital period of about 457 days. This suggests that the system was likely formed through stable Roche lobe overflow (RLOF). A kinematic analysis shows that EC 22536-5304 is on an eccentric orbit around the Galactic centre. This, as well as the low metallicity and strong alpha enhancement of the sdF-type companion, indicate that EC 22536-5304 is part of the Galactic halo or metal-weak thick disc. As the first long-period hot subdwarf binary at [FE/H] less than or similar to- 1, EC 22536-5304 may help to constrain the RLOF mechanism for mass transfer from low-mass, low-metallicity red giant branch (RGB) stars to main-sequence companions. KW - stars: abundances KW - stars: chemically peculiar KW - subdwarfs KW - stars: individual: EC 22536-5304 KW - binaries: spectroscopic Y1 - 2021 U6 - https://doi.org/10.1051/0004-6361/202141381 SN - 1432-0746 VL - 653 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Andersson, Edvin K. W. A1 - Sångeland, Christofer A1 - Berggren, Elin A1 - Johansson, Fredrik O. L. A1 - Kühn, Danilo A1 - Lindblad, Andreas A1 - Mindemark, Jonas A1 - Hahlin, Maria T1 - Early-stage decomposition of solid polymer electrolytes in Li-metal batteries JF - Journal of materials chemistry : A, Materials for energy and sustainability N2 - Development of functional and stable solid polymer electrolytes (SPEs) for battery applications is an important step towards both safer batteries and for the realization of lithium-based or anode-less batteries. The interface between the lithium and the solid polymer electrolyte is one of the bottlenecks, where severe degradation is expected. Here, the stability of three different SPEs - poly(ethylene oxide) (PEO), poly(epsilon-caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC) - together with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, is investigated after they have been exposed to lithium metal under UHV conditions. Degradation compounds, e.g. Li-O-R, LiF and LixSyOz, are identified for all SPEs using soft X-ray photoelectron spectroscopy. A competing degradation between polymer and salt is identified in the outermost surface region (<7 nm), and is dependent on the polymer host. PTMC:LiTFSI shows the most severe decomposition of both polymer and salt followed by PCL:LiTFSI and PEO:LiTFSI. In addition, the movement of lithium species through the decomposed interface shows large variation depending on the polymer electrolyte system. Y1 - 2021 U6 - https://doi.org/10.1039/d1ta05015j SN - 2050-7488 SN - 2050-7496 VL - 9 IS - 39 SP - 22462 EP - 22471 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Wang, Wei A1 - Cherstvy, Andrey G. A1 - Kantz, Holger A1 - Metzler, Ralf A1 - Sokolov, Igor M. T1 - Time averaging and emerging nonergodicity upon resetting of fractional Brownian motion and heterogeneous diffusion processes JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - How different are the results of constant-rate resetting of anomalous-diffusion processes in terms of their ensemble-averaged versus time-averaged mean-squared displacements (MSDs versus TAMSDs) and how does stochastic resetting impact nonergodicity? We examine, both analytically and by simulations, the implications of resetting on the MSD- and TAMSD-based spreading dynamics of particles executing fractional Brownian motion (FBM) with a long-time memory, heterogeneous diffusion processes (HDPs) with a power-law space-dependent diffusivity D(x) = D0|x|gamma and their "combined" process of HDP-FBM. We find, inter alia, that the resetting dynamics of originally ergodic FBM for superdiffusive Hurst exponents develops disparities in scaling and magnitudes of the MSDs and mean TAMSDs indicating weak ergodicity breaking. For subdiffusive HDPs we also quantify the nonequivalence of the MSD and TAMSD and observe a new trimodal form of the probability density function. For reset FBM, HDPs and HDP-FBM we compute analytically and verify by simulations the short-time MSD and TAMSD asymptotes and long-time plateaus reminiscent of those for processes under confinement. We show that certain characteristics of these reset processes are functionally similar despite a different stochastic nature of their nonreset variants. Importantly, we discover nonmonotonicity of the ergodicitybreaking parameter EB as a function of the resetting rate r. For all reset processes studied we unveil a pronounced resetting-induced nonergodicity with a maximum of EB at intermediate r and EB similar to(1/r )-decay at large r. Alongside the emerging MSD-versus-TAMSD disparity, this r-dependence of EB can be an experimentally testable prediction. We conclude by discussing some implications to experimental systems featuring resetting dynamics. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevE.104.024105 SN - 2470-0045 SN - 2470-0053 VL - 104 IS - 2 PB - American Institute of Physics CY - Woodbury, NY ER - TY - JOUR A1 - Kurilovich, Aleksandr A. A1 - Mantsevich, Vladimir N. A1 - Mardoukhi, Yousof A1 - Stevenson, Keith J. A1 - Chechkin, Aleksei A1 - Palyulin, Vladimir V. T1 - Non-Markovian diffusion of excitons in layered perovskites and transition metal dichalcogenides JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - The diffusion of excitons in perovskites and transition metal dichalcogenides shows clear anomalous, subdiffusive behaviour in experiments. In this paper we develop a non-Markovian mobile-immobile model which provides an explanation of this behaviour through paired theoretical and simulation approaches. The simulation model is based on a random walk on a 2D lattice with randomly distributed deep traps such that the trapping time distribution involves slowly decaying power-law asymptotics. The theoretical model uses coupled diffusion and rate equations for free and trapped excitons, respectively, with an integral term responsible for trapping. The model provides a good fitting of the experimental data, thus, showing a way for quantifying the exciton diffusion dynamics. Y1 - 2022 U6 - https://doi.org/10.1039/d2cp00557c SN - 1463-9076 SN - 1463-9084 VL - 24 IS - 22 SP - 13941 EP - 13950 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Grischek, Max A1 - Caprioglio, Pietro A1 - Zhang, Jiahuan A1 - Pena-Camargo, Francisco A1 - Sveinbjornsson, Kari A1 - Zu, Fengshuo A1 - Menzel, Dorothee A1 - Warby, Jonathan H. A1 - Li, Jinzhao A1 - Koch, Norbert A1 - Unger, Eva A1 - Korte, Lars A1 - Neher, Dieter A1 - Stolterfoht, Martin A1 - Albrecht, Steve T1 - Efficiency Potential and Voltage Loss of Inorganic CsPbI2Br Perovskite Solar Cells JF - Solar RRL N2 - Inorganic perovskite solar cells show excellent thermal stability, but the reported power conversion efficiencies are still lower than for organic-inorganic perovskites. This is mainly caused by lower open-circuit voltages (V(OC)s). Herein, the reasons for the low V-OC in inorganic CsPbI2Br perovskite solar cells are investigated. Intensity-dependent photoluminescence measurements for different layer stacks reveal that n-i-p and p-i-n CsPbI2Br solar cells exhibit a strong mismatch between quasi-Fermi level splitting (QFLS) and V-OC. Specifically, the CsPbI2Br p-i-n perovskite solar cell has a QFLS-e center dot V-OC mismatch of 179 meV, compared with 11 meV for a reference cell with an organic-inorganic perovskite of similar bandgap. On the other hand, this study shows that the CsPbI2Br films with a bandgap of 1.9 eV have a very low defect density, resulting in an efficiency potential of 20.3% with a MeO-2PACz hole-transporting layer and 20.8% on compact TiO2. Using ultraviolet photoelectron spectroscopy measurements, energy level misalignment is identified as a possible reason for the QFLS-e center dot V-OC mismatch and strategies for overcoming this V-OC limitation are discussed. This work highlights the need to control the interfacial energetics in inorganic perovskite solar cells, but also gives promise for high efficiencies once this issue is resolved. KW - CsPbI2Br KW - efficiency potentials KW - inorganic perovskites KW - photoluminescence KW - solar cells KW - voltage losses Y1 - 2022 U6 - https://doi.org/10.1002/solr.202200690 SN - 2367-198X VL - 6 IS - 11 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Caesar, Levke A1 - McCarthy, Gerard D. A1 - Thornalley, David J. R. A1 - Cahill, Niamh A1 - Rahmstorf, Stefan T1 - Reply to: Atlantic circulation change still uncertain T2 - Nature geoscience Y1 - 2022 U6 - https://doi.org/10.1038/s41561-022-00897-3 SN - 1752-0894 SN - 1752-0908 VL - 15 IS - 3 SP - 168 EP - 170 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Lepri, Stefano A1 - Pikovsky, Arkady T1 - Phase-locking dynamics of heterogeneous oscillator arrays JF - Chaos, solitons & fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science N2 - We consider an array of nearest-neighbor coupled nonlinear autonomous oscillators with quenched ran-dom frequencies and purely conservative coupling. We show that global phase-locked states emerge in finite lattices and study numerically their destruction. Upon change of model parameters, such states are found to become unstable with the generation of localized periodic and chaotic oscillations. For weak nonlinear frequency dispersion, metastability occur akin to the case of almost-conservative systems. We also compare the results with the phase-approximation in which the amplitude dynamics is adiabatically eliminated. KW - Ginzburg-Landau lattice KW - Disorder KW - Localized chaos KW - Reactive coupling Y1 - 2022 U6 - https://doi.org/10.1016/j.chaos.2021.111721 SN - 0960-0779 SN - 1873-2887 VL - 155 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Morris, Paul J. A1 - Bohdan, Artem A1 - Weidl, Martin S. A1 - Tsirou, Michelle A1 - Fulat, Karol A1 - Pohl, Martin T1 - Pre-acceleration in the electron foreshock. II. oblique whistler waves JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Thermal electrons have gyroradii many orders of magnitude smaller than the finite width of a shock, thus need to be pre-accelerated before they can cross it and be accelerated by diffusive shock acceleration. One region where pre-acceleration may occur is the inner foreshock, which upstream electrons must pass through before any potential downstream crossing. In this paper, we perform a large-scale particle-in-cell simulation that generates a single shock with parameters motivated from supernova remnants. Within the foreshock, reflected electrons excite the oblique whistler instability and produce electromagnetic whistler waves, which comove with the upstream flow and as nonlinear structures eventually reach radii of up to 5 ion-gyroradii. We show that the inner electromagnetic configuration of the whistlers evolves into complex nonlinear structures bound by a strong magnetic field around four times the upstream value. Although these nonlinear structures do not in general interact with cospatial upstream electrons, they resonate with electrons that have been reflected at the shock. We show that they can scatter, or even trap, reflected electrons, confining around 0.8% of the total upstream electron population to the region close to the shock where they can undergo substantial pre-acceleration. This acceleration process is similar to, yet approximately three times more efficient than, stochastic shock drift acceleration. Y1 - 2023 U6 - https://doi.org/10.3847/1538-4357/acaec8 SN - 0004-637X SN - 1538-4357 VL - 944 IS - 1 PB - Institute of Physics Publ. CY - London ER - TY - JOUR A1 - Pena-Camargo, Francisco A1 - Thiesbrummel, Jarla A1 - Hempel, Hannes A1 - Musiienko, Artem A1 - Le Corre, Vincent M. A1 - Diekmann, Jonas A1 - Warby, Jonathan A1 - Unold, Thomas A1 - Lang, Felix A1 - Neher, Dieter A1 - Stolterfoht, Martin T1 - Revealing the doping density in perovskite solar cells and its impact on device performance JF - Applied physics reviews N2 - Traditional inorganic semiconductors can be electronically doped with high precision. Conversely, there is still conjecture regarding the assessment of the electronic doping density in metal-halide perovskites, not to mention of a control thereof. This paper presents a multifaceted approach to determine the electronic doping density for a range of different lead-halide perovskite systems. Optical and electrical characterization techniques, comprising intensity-dependent and transient photoluminescence, AC Hall effect, transfer-length-methods, and charge extraction measurements were instrumental in quantifying an upper limit for the doping density. The obtained values are subsequently compared to the electrode charge per cell volume under short-circuit conditions ( CUbi/eV), which amounts to roughly 10(16) cm(-3). This figure of merit represents the critical limit below which doping-induced charges do not influence the device performance. The experimental results consistently demonstrate that the doping density is below this critical threshold 10(12) cm(-3), which means << CUbi / e V) for all common lead-based metal-halide perovskites. Nevertheless, although the density of doping-induced charges is too low to redistribute the built-in voltage in the perovskite active layer, mobile ions are present in sufficient quantities to create space-charge-regions in the active layer, reminiscent of doped pn-junctions. These results are well supported by drift-diffusion simulations, which confirm that the device performance is not affected by such low doping densities. Y1 - 2022 U6 - https://doi.org/10.1063/5.0085286 SN - 1931-9401 VL - 9 IS - 2 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Dudi, Reetika A1 - Dietrich, Tim A1 - Rashti, Alireza A1 - Brügmann, Bernd A1 - Steinhoff, Jan A1 - Tichy, Wolfgang T1 - High-accuracy simulations of highly spinning binary neutron star systems JF - Physical review : D, Particles, fields, gravitation, and cosmology N2 - With an increasing number of expected gravitational-wave detections of binary neutron star mergers, it is essential that gravitational-wave models employed for the analysis of observational data are able to describe generic compact binary systems. This includes systems in which the individual neutron stars are millisecond pulsars for which spin effects become essential. In this work, we perform numerical-relativity simulations of binary neutron stars with aligned and antialigned spins within a range of dimensionless spins of chi similar to [-0.28, 0.58]. The simulations are performed with multiple resolutions, show a clear convergence order and, consequently, can be used to test existing waveform approximants. We find that for very high spins gravitational-wave models that have been employed for the interpretation of GW170817 and GW190425 arc not capable of describing our numerical-relativity dataset. We verify through a full parameter estimation study in which clear biases in the estimate of the tidal deformability and effective spin are present. We hope that in preparation of the next gravitational-wave observing run of the Advanced LIGO and Advanced Virgo detectors our new set of numerical-relativity data can be used to support future developments of new gravitational-wave models. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevD.105.064050 SN - 2470-0010 SN - 2470-0029 VL - 105 IS - 6 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Pohl, Martin A1 - Macias, Oscar A1 - Coleman, Phaedra A1 - Gordon, Chris T1 - Assessing the impact of hydrogen absorption on the characteristics of the Galactic center excess JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present a new reconstruction of the distribution of atomic hydrogen in the inner Galaxy that is based on explicit radiation transport modeling of line and continuum emission and a gas-flow model in the barred Galaxy that provides distance resolution for lines of sight toward the Galactic center. The main benefits of the new gas model are (a) the ability to reproduce the negative line signals seen with the HI4PI survey and (b) the accounting for gas that primarily manifests itself through absorption. We apply the new model of Galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner Galaxy, for which an excess at a few GeV was reported that may be related to dark matter. We find with high significance an improved fit to the diffuse gamma-ray emission observed with the Fermi-LAT, if our new H i model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. The fit still requires a nuclear bulge at high significance. Once this is included there is no evidence of a dark-matter signal, be it cuspy or cored. But an additional so-called boxy bulge is still favored by the data. This finding is robust under the variation of various parameters, for example, the excitation temperature of atomic hydrogen, and a number of tests for systematic issues. Y1 - 2022 U6 - https://doi.org/10.3847/1538-4357/ac6032 SN - 0004-637X SN - 1538-4357 VL - 929 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Stegemann, Robert A1 - Lyamkin, Viktor A1 - Cabeza, Sandra A1 - Evsevleev, Sergei A1 - Pelkner, Matthias A1 - Bruno, Giovanni T1 - Subsurface and bulk residual stress analysis of S235JRC+C Steel TIG weld by diffraction and magnetic stray field measurements JF - Experimental mechanics : an international journal of the Society for Experimental Mechanics N2 - Background Due to physical coupling between mechanical stress and magnetization in ferromagnetic materials, it is assumed in the literature that the distribution of the magnetic stray field corresponds to the internal (residual) stress of the specimen. The correlation is, however, not trivial, since the magnetic stray field is also influenced by the microstructure and the geometry of component. The understanding of the correlation between residual stress and magnetic stray field could help to evaluate the integrity of welded components. Objective This study aims at understanding the possible correlation of subsurface and bulk residual stress with magnetic stray field in a low carbon steel weld. Methods The residual stress was determined by synchrotron X-ray diffraction (SXRD, subsurface region) and by neutron diffraction (ND, bulk region). SXRD possesses a higher spatial resolution than ND. Magnetic stray fields were mapped by utilizing high-spatial-resolution giant magneto resistance (GMR) sensors. Results The subsurface residual stress overall correlates better with the magnetic stray field distribution than the bulk stress. This correlation is especially visible in the regions outside the heat affected zone, where the influence of the microstructural features is less pronounced but steep residual stress gradients are present. Conclusions It was demonstrated that the localized stray field sources without any obvious microstructural variations are associated with steep stress gradients. The good correlation between subsurface residual stress and magnetic signal indicates that the source of the magnetic stray fields is to be found in the range of the penetration depth of the SXRD measurements. KW - residual stress KW - magnetic stray field KW - synchrotron X-ray diffraction KW - neutron diffraction KW - TIG-welding Y1 - 2022 U6 - https://doi.org/10.1007/s11340-022-00841-x SN - 0014-4851 SN - 1741-2765 VL - 62 IS - 6 SP - 1017 EP - 1025 PB - Springer CY - New York ER - TY - JOUR A1 - Ashton, Gregory A1 - Dietrich, Tim T1 - The use of hypermodels to understand binary neutron star collisions JF - Nature astronomy N2 - Gravitational waves from the collision of binary neutron stars provide a unique opportunity to study the behaviour of supranuclear matter, the fundamental properties of gravity and the cosmic history of our Universe. However, given the complexity of Einstein's field equations, theoretical models that enable source-property inference suffer from systematic uncertainties due to simplifying assumptions. We develop a hypermodel approach to compare and measure the uncertainty of gravitational-wave approximants. Using state-of-the-art models, we apply this new technique to the binary neutron star observations GW170817 and GW190425 and to the sub-threshold candidate GW200311_103121. Our analysis reveals subtle systematic differences (with Bayesian odds of similar to 2) between waveform models. A frequency-dependence study suggests that this may be due to the treatment of the tidal sector. This new technique provides a proving ground for model development and a means to identify waveform systematics in future observing runs where detector improvements will increase the number and clarity of binary neutron star collisions we observe. Y1 - 2022 U6 - https://doi.org/10.1038/s41550-022-01707-x SN - 2397-3366 VL - 6 IS - 8 SP - 961 EP - 967 PB - Nature portfolio CY - Berlin ER - TY - JOUR A1 - Nakoudi, Konstantina A1 - Stachlewska, Iwona S. A1 - Ritter, Christoph T1 - An extended lidar-based cirrus cloud retrieval scheme BT - first application over an Arctic site JF - Optics express : the international electronic journal of optics / Optica N2 - Accurate and precise characterization of cirrus cloud geometrical and optical properties is essential for better constraining their radiative footprint. A lidar-based retrieval scheme is proposed here, with its performance assessed on fine spatio-temporal observations over the Arctic site of Ny-Alesund, Svalbard. Two contributions related to cirrus geometrical (dynamic Wavelet Covariance Transform (WCT)) and optical properties (constrained Klett) are reported. The dynamic WCT rendered cirrus detection more robust, especially for thin cirrus layers that frequently remained undetected by the classical WCT method. Regarding optical characterization, we developed an iterative scheme for determining the cirrus lidar ratio (LRci) that is a crucial parameter for aerosol - cloud discrimination. Building upon the Klett-Fernald method, the LRci was constrained by an additional reference value. In established methods, such as the double-ended Klett, an aerosol-free reference value is applied. In the proposed constrained Klett, however, the reference value was approximated from cloud-free or low cloud optical depth (COD up to 0.2) profiles and proved to agree with independent Raman estimates. For optically thin cirrus, the constrained Klett inherent uncertainties reached 50% (60-74%) in terms of COD (LRci). However, for opaque cirrus COD (LRci) uncertainties were lower than 10% (15%). The detection method discrepancies (dynamic versus static WCT) had a higher impact on the optical properties of low COD layers (up to 90%) compared to optically thicker ones (less than 10%). The constrained Klett presented high agreement with two established retrievals. For an exemplary cirrus cloud, the constrained Klett estimated the COD355 (LRci355) at 0.28 +/- 0.17 (29 +/- 4 sr), the double-ended Klett at 0.27 +/- 0.15 (32 +/- 4 sr) and the Raman retrievals at 0.22 +/- 0.12 (26 +/- 11 sr). Our approach to determine the necessary reference value can also be applied in established methods and increase their accuracy. In contrast, the classical aerosol-free assumption led to 44 sr LRci overestimation in optically thin layers and 2-8 sr in thicker ones. The multiple scattering effect was corrected using Eloranta (1998) and accounted for 50-60% extinction underestimation near the cloud base and 20-30% within the cirrus layers. Y1 - 2021 U6 - https://doi.org/10.1364/OE.414770 SN - 1094-4087 VL - 29 IS - 6 SP - 8553 EP - 8580 PB - Optical Society of America CY - Washington ER - TY - JOUR A1 - Ramos-Larios, Gerardo A1 - Toala, Jesús Alberto A1 - Rodriguez-Gonzalez, Janis B. A1 - Guerrero, Martin A. A1 - Gomez-Gonzalez, Víctor Mauricio Alfonso T1 - Rings and arcs around evolved stars - III. Physical conditions of the ring-like structures in the planetary nebula IC 4406 revealed by MUSE JF - Monthly notices of the Royal Astronomical Society N2 - We present the analysis of Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least five ring-like structures north and south of the main nebula of IC4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (n(e)), and temperature (T-e). The rings are found to have similar T-e as the rim of the main nebula, but smaller n(e). Ratios between different ionic species suggest that the rings of IC4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC 6543, the Cat's Eye Nebula. KW - stars: evolution KW - stars: winds, outflows KW - planetary nebulae: general; KW - planetary nebulae: individual: IC4406 Y1 - 2022 SN - 0035-8711 SN - 1365-2966 VL - 513 IS - 2 SP - 2862 EP - 2868 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - van Marle, Allard Jan A1 - Bohdan, Artem A1 - Morris, Paul J. A1 - Pohl, Martin A1 - Marcowith, Alexandre T1 - Diffusive shock acceleration at oblique high mach number shocks JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The current paradigm of cosmic-ray (CR) origin states that the greater part of galactic CRs is produced by supernova remnants. The interaction of supernova ejecta with the interstellar medium after a supernova's explosions results in shocks responsible for CR acceleration via diffusive shock acceleration (DSA). We use particle-in-cell (PIC) simulations and a combined PIC-magnetohydrodynamic (PIC-MHD) technique to investigate whether DSA can occur in oblique high Mach number shocks. Using the PIC method, we follow the formation of the shock and determine the fraction of the particles that gets involved in DSA. With this result, we use PIC-MHD simulations to model the large-scale structure of the plasma and the magnetic field surrounding the shock and find out whether or not the reflected particles can generate upstream turbulence and trigger DSA. We find that the feasibility of this process in oblique shocks depends strongly on the Alfvenic Mach number, and the DSA process is more likely to be triggered at high Mach number shocks. Y1 - 2022 U6 - https://doi.org/10.3847/1538-4357/ac5962 SN - 1538-4357 VL - 929 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Wiebeler, Christian A1 - Vollbrecht, Joachim A1 - Neuba, Adam A1 - Kitzerow, Heinz A1 - Schumacher, Stefan T1 - Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters JF - Scientific reports N2 - A detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree-Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands. Y1 - 2021 U6 - https://doi.org/10.1038/s41598-021-95551-0 SN - 2045-2322 VL - 11 IS - 1 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - JOUR A1 - Sidoli, Lara A1 - Sguera, Vito A1 - Esposito, Paolo A1 - Oskinova, Lida A1 - Polletta, Maria del Carmen T1 - XMM-Newton discovery of very high obscuration in the candidate Supergiant Fast X-ray Transient AX J1714.1-3912 JF - Monthly notices of the Royal Astronomical Society N2 - We have analysed an archival XMM-Newton EPIC observation that serendipitously covered the sky position of a variable X-ray source AX J1714.1-3912, previously suggested to be a Supergiant Fast X-ray Transient (SFXT). During the XMM-Newton observation the source is variable on a timescale of hundred seconds and shows two luminosity states, with a flaring activity followed by unflared emission, with a variability amplitude of a factor of about 50. We have discovered an intense iron emission line with a centroid energy of 6.4 keV in the power law-like spectrum, modified by a large absorption (N-H similar to 10(24) cm(-2)), never observed before from this source. This X-ray spectrum is unusual for an SFXT, but resembles the so-called 'highly obscured sources', high mass X-ray binaries (HMXBs) hosting an evolved B[e] supergiant companion (sgB[e]). This might suggest that AX J1714.1-3912 is a new member of this rare type of HMXBs, which includes IGR J16318-4848 and CI Camelopardalis. Increasing this small population of sources would be remarkable, as they represent an interesting short transition evolutionary stage in the evolution of massive binaries. Nevertheless, AX J1714.1-3912 appears to share X-ray properties of both kinds of HMXBs (SFXT versus sgB[e] HMXB). Therefore, further investigations of the companion star are needed to disentangle the two hypothesis. KW - X-rays: binaries KW - X-rays: individual: AX J1714.1-3912 Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac691 SN - 0035-8711 SN - 1365-2966 VL - 512 IS - 2 SP - 2929 EP - 2935 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Wolff, Nora A1 - Klimm, Detlef A1 - Habicht, Klaus A1 - Fritsch, Katharina T1 - Crystal growth and thermodynamic investigation of Bi2M2+O4 (M = Pd, Cu) JF - CrystEngComm / The Royal Society of Chemistry N2 - Phase equilibria that are relevant for the growth of Bi2MO4 have been studied experimentally, and the ternary phase diagrams of Bi2O3-PdO2-Pd and Bi2O3-Cu2O-CuO and its isopleth section Bi2O3-CuO were redetermined. It is shown that every melting and crystallization process is always accompanied by a redox process at the phase boundary and that for both title compounds, the valence of the transition metal is lowered during melting. Vice versa, during crystal growth, O-2 must be transported through the melt to the phase boundary. Based on these new insights provided by our thermodynamic studies, Bi2CuO4 single crystals with a length of up to 7 cm and a diameter of 6 mm were grown by the OFZ technique to be used for investigations of magnetic, electronic and thermal transport properties. The grown crystals were characterized by powder X-ray diffraction, Laue, magnetization and specific heat measurements. Y1 - 2021 U6 - https://doi.org/10.1039/d1ce00220a SN - 1466-8033 VL - 23 IS - 17 SP - 3230 EP - 3238 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Bernardi, Rafael L. A1 - Berdja, Amokrane A1 - Dani Guzman, Christian A1 - Torres-Torriti, Miguel A1 - Roth, Martin M. T1 - Restoration of images with a spatially varying PSF of the T80-S telescope optical model using neural networks JF - Monthly notices of the Royal Astronomical Society N2 - Most image restoration methods in astronomy rely upon probabilistic tools that infer the best solution for a deconvolution problem. They achieve good performances when the point spread function (PSF) is spatially invariant in the image plane. However, this condition is not always satisfied in real optical systems. We propose a new method for the restoration of images affected by static and anisotropic aberrations using Deep Neural Networks that can be directly applied to sky images. The network is trained using simulated sky images corresponding to the T80-S Telescope optical model, a 80-cm survey imager at Cerro Tololo (Chile), which are synthesized using a Zernike polynomial representation of the optical system. Once trained, the network can be used directly on sky images, outputting a corrected version of the image that has a constant and known PSF across its field of view. The method is to be tested on the T80-S Telescope. We present the method and results on synthetic data. KW - methods: statistical KW - techniques: image processing Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab3400 SN - 0035-8711 SN - 1365-2966 VL - 510 IS - 3 SP - 4284 EP - 4294 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Riese, Josef A1 - Vogelsang, Christoph A1 - Schröder, Jan A1 - Borowski, Andreas A1 - Kulgemeyer, Christoph A1 - Reinhold, Peter A1 - Schecker, Horst T1 - The development of lesson planning skills in the subject of physics T1 - Entwicklung von Unterrichtsplanungsfähigkeit im Fach Physik BT - What influence does professional knowledge have? BT - Welchen Einfluss hat Professionswissen? JF - Zeitschrift für Erziehungswissenschaft N2 - One main goal of university teacher education is the first acquisition of skills for theory-driven lesson planning. According to models of teachers' professional competence, it is assumed that the acquired professional knowledge represents an essential basis for the development of planning skills. Learning opportunities to apply this professional knowledge often occur in school internships, usually in advanced semesters of teacher education programs. It is also assumed that practical experience within lesson planning supports the formation of professional knowledge. However, the relationship between the extent of professional knowledge and the development of skills to plan a lesson lacks evidence. There is a particular challenge in measuring lesson planning skills both authentically and standardized. To evaluate the mentioned relationship, a longitudinal pre-post-study with prospective physics-teachers (N = 68 in the longitudinal section) was conducted at four German universities. Pre-service physics teachers' skills to plan a lesson were assessed with a standardized performance assessment at the beginning and at the end of a longterm-internship. This assessment consists of planning a physics lesson, conveying Newton's third Law, in a simulated and standardized way with limited time. In addition, content knowledge, pedagogical content knowledge and pedagogical knowledge has been assessed using standardized instruments. Furthermore, additional information about the internship and the amount of learning opportunities was collected at the end of the internship. During the internship, both lesson planning skills and all components of professional knowledge increased. Cross-Lagged-Panel-Analyses reveal that in particular pre-service teachers' pedagogical content knowledge as well as pedagogical knowledge at the beginning of the internship influences the development of lesson planning skills. N2 - Im Lehramtsstudium sollen Studierende grundlegende Fähigkeiten zur theoriegeleiteten Unterrichtsplanung erwerben. In Übereinstimmung mit Modellen zur professionellen Handlungskompetenz von Lehrkräften wird hierbei meist angenommen, dass das im Studienverlauf erworbene Professionswissen eine wesentliche Grundlage für den Aufbau von Fähigkeiten zur Unterrichtsplanung bildet. Lerngelegenheiten zur Anwendung dieses Professionswissens bieten vor allem schulpraktische Phasen im fortgeschrittenen Studienverlauf. Es wird aber ebenso angenommen, dass gerade Erfahrungen mit der Unterrichtsplanung den Aufbau von Professionswissen unterstützen. Der Zusammenhang zwischen dem Ausmaß des Professionswissens und der Entwicklung von Planungsfähigkeit ist bisher unzureichend empirisch geklärt. Eine besondere methodische Herausforderung besteht darin, Planungsfähigkeiten sowohl möglichst authentisch als auch auf standardisierte Weise zu erfassen. Zur Untersuchung des genannten Zusammenhangs wurde eine längsschnittliche Studie im Prä-Post-Design bei angehenden Physiklehrkräften (N = 68 im Längsschnitt) an vier Universitäten durchgeführt. Die Unterrichtsplanungsfähigkeit wurde mit Hilfe eines standardisierten Performanztests vor und nach dem Absolvieren eines Praxissemesters erfasst, indem als Standardsituation der Entwurf einer Unterrichtsstunde zum 3. Newton’schen Axiom unter definierten Zeitvorgaben im Praxissemester simuliert wurde. Zusätzlich wurden das fachliche, fachdidaktische und pädagogische Wissen der Studierenden mit Hilfe standardisierter Instrumente zu beiden Zeitpunkten erhoben, sowie die einschlägigen Lerngelegenheiten im Praxissemester über einen Fragebogen erfasst. Sowohl für Unterrichtsplanungsfähigkeit als auch für alle Wissensvariablen können Zuwächse im Praxissemester beobachtet werden. Cross-Lagged-Panel-Analysen zeigen, dass insbesondere die Ausprägung des fachdidaktischen und pädagogischen Wissens der Studierenden am Beginn des Praxissemesters die Entwicklung von Unterrichtsplanungsfähigkeit begünstigt. KW - teacher education KW - physics KW - lesson planning KW - performance assessment KW - professional knowledge KW - longitudinal study KW - Lehrerbildung KW - Physik KW - Unterrichtsplanung KW - Performanztest KW - Professionswissen KW - Längsschnittstudie Y1 - 2022 U6 - https://doi.org/10.1007/s11618-022-01112-0 SN - 1434-663X SN - 1862-5215 IS - 4 SP - 843 EP - 867 PB - Springer VS/Springer Fachmedien Wiesbaden GmbH CY - Wiesbaden ER - TY - JOUR A1 - Bozzo, Enrico A1 - Ferrigno, Carlo A1 - Oskinova, Lida A1 - Ducci, Lorenzo T1 - Accretion of a clumped wind from a red supergiant donor on to a magnetar is suggested by the analysis of the XMM-Newton and NuSTAR observations of the X-ray binary 3A 1954+319 JF - Monthly notices of the Royal Astronomical Society N2 - 3A 1954+319 has been classified for a long time as a symbiotic X-ray binary, hosting a slowly rotating neutron star and an aged M red giant. Recently, this classification has been revised thanks to the discovery that the donor star is an M supergiant. This makes 3A 1954+319 a rare type of high-mass X-ray binary consisting of a neutron star and a red supergiant donor. In this paper, we analyse two archival and still unpublished XMM-Newton and NuSTAR observations of the source. We perform a detailed hardness ratio-resolved spectral analysis to search for spectral variability that could help investigating the structures of the inhomogeneous M supergiant wind from which the neutron star is accreting. We discuss our results in the context of wind-fed supergiant X-ray binaries and show that the newest findings on 3A 1954+319 reinforce the hypothesis that the neutron star in this system is endowed with a magnetar-like magnetic field strength (greater than or similar to 10(14) G). KW - accretion KW - stars: massive KW - stars: neutron KW - X-rays: binaries KW - X-rays: individual: 3A 1954+319 KW - X-rays: stars KW - accretion discs Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab3688 SN - 0035-8711 SN - 1365-2966 VL - 510 IS - 3 SP - 4645 EP - 4653 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Raoufi, Meysam A1 - Hörmann, Ulrich A1 - Ligorio, Giovanni A1 - Hildebrandt, Jana A1 - Pätzel, Michael A1 - Schultz, Thorsten A1 - Perdigon-Toro, Lorena A1 - Koch, Norbert A1 - List-Kratochvil, Emil A1 - Hecht, Stefan A1 - Neher, Dieter T1 - Simultaneous effect of ultraviolet radiation and surface modification on the work function and hole injection properties of ZnO thin films JF - Physica Status Solidi. A , Applications and materials science N2 - The combined effect of ultraviolet (UV) light soaking and self-assembled monolayer deposition on the work function (WF) of thin ZnO layers and on the efficiency of hole injection into the prototypical conjugated polymer poly(3-hexylthiophen-2,5-diyl) (P3HT) is systematically investigated. It is shown that the WF and injection efficiency depend strongly on the history of UV light exposure. Proper treatment of the ZnO layer enables ohmic hole injection into P3HT, demonstrating ZnO as a potential anode material for organic optoelectronic devices. The results also suggest that valid conclusions on the energy-level alignment at the ZnO/organic interfaces may only be drawn if the illumination history is precisely known and controlled. This is inherently problematic when comparing electronic data from ultraviolet photoelectron spectroscopy (UPS) measurements carried out under different or ill-defined illumination conditions. KW - charge injection across hybrid interfaces KW - energy-level alignments KW - hybrid metal oxides KW - organic interfaces Y1 - 2020 U6 - https://doi.org/10.1002/pssa.201900876 SN - 1862-6300 SN - 1862-6319 VL - 217 IS - 5 SP - 1 EP - 6 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mösenlechner, Gerald A1 - Paunzen, Ernst A1 - Pelisoli, Ingrid D. A1 - Seelig, Joseph A1 - Stidl, Sarah A1 - Maitzen, Hans Michael T1 - A Kepler K2 view of subdwarf A-type stars JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The spectroscopic class of subdwarf A-type (sdA) stars has come into focus in recent years because of their possible link to extremely low-mass white dwarfs, a rare class of objects resulting from binary evolution. Although most sdA stars are consistent with metal-poor halo main-sequence stars, the formation and evolution of a fraction of these stars are still matters of debate. Aims. The identification of photometric variability can help to put further constraints on the evolutionary status of sdA stars, in particular through the analysis of pulsations. Moreover, the binary ratio, which can be deduced from eclipsing binaries and ellipsoidal variables, is important as input for stellar models. In order to search for variability due to either binarity or pulsations in objects of the spectroscopic sdA class, we have extracted all available high precision light curves from the Kepler K2 mission. Methods. We have performed a thorough time series analysis on all available light curves, employing three different methods. Frequencies with a signal-to-noise ratio higher than four have been used for further analysis. Results. From the 25 targets, 13 turned out to be variables of different kinds (i.e., classical pulsating stars, ellipsoidal and cataclysmic variables, eclipsing binaries, and rotationally induced variables). For the remaining 12 objects, a variability threshold was determined. KW - subdwarfs KW - white dwarfs KW - binaries: general KW - stars: evolution KW - stars: variables: general Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202037789 SN - 0004-6361 SN - 1432-0746 VL - 657 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Johansson, Fredrik O. L. A1 - Leitner, Torsten A1 - Bidermane, Ieva A1 - Born, Artur A1 - Föhlisch, Alexander A1 - Svensson, Svante A1 - Mårtensson, Nils A1 - Lindblad, Andreas T1 - Auger- and photoelectron coincidences of molecular O2 adsorbed on Ag(111) JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - The oxygen on Ag(111) system has been investigated with Auger electron-photoelectron coincidence spectroscopy (APECS). The coincidence spectra between O 1s core level photoelectrons and O KLL Auger electrons have been studied together with Ag(3)d/AgM4,5NN coincidences. We also describe the electron-electron coincidence spectrometer setup, CoESCA, consisting of two angle resolved time-of-flight spectrometers at a synchrotron light source. Contributions from molecular oxygen and chemisorbed oxygen are assigned using the coincidence data, conclusions are drawn primarily from the O 1s/O KLL data. The data acquisition and treatment procedure are also outlined. The chemisorbed oxygen species observed are relevant for the catalytic ethylene oxidation. KW - oxygen/Ag(111) KW - Auger electron KW - photoelectron KW - coincidence KW - APECS KW - spectroscopy Y1 - 2022 U6 - https://doi.org/10.1016/j.elspec.2022.147174 SN - 0368-2048 SN - 1873-2526 VL - 256 PB - Elsevier CY - New York, NY [u.a.] ER - TY - JOUR A1 - Doerries, Timo J. A1 - Chechkin, Aleksei A1 - Schumer, Rina A1 - Metzler, Ralf T1 - Rate equations, spatial moments, and concentration profiles for mobile-immobile models with power-law and mixed waiting time distributions JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We present a framework for systems in which diffusion-advection transport of a tracer substance in a mobile zone is interrupted by trapping in an immobile zone. Our model unifies different model approaches based on distributed-order diffusion equations, exciton diffusion rate models, and random-walk models for multirate mobile-immobile mass transport. We study various forms for the trapping time dynamics and their effects on the tracer mass in the mobile zone. Moreover, we find the associated breakthrough curves, the tracer density at a fixed point in space as a function of time, and the mobile and immobile concentration profiles and the respective moments of the transport. Specifically, we derive explicit forms for the anomalous transport dynamics and an asymptotic power-law decay of the mobile mass for a Mittag-Leffler trapping time distribution. In our analysis we point out that even for exponential trapping time densities, transient anomalous transport is observed. Our results have direct applications in geophysical contexts, but also in biological, soft matter, and solid state systems. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevE.105.014105 SN - 2470-0045 SN - 2470-0053 SN - 2470-0061 VL - 105 IS - 1 PB - The American Institute of Physics CY - Woodbury, NY ER - TY - JOUR A1 - Sprengel, Maximilian A1 - Mohr, Gunther A1 - Altenburg, Simon J. A1 - Evans, Alexander A1 - Serrano-Munoz, Itziar A1 - Kromm, Arne A1 - Pirling, Thilo A1 - Bruno, Giovanni A1 - Kannengießer, Thomas T1 - Triaxial residual stress in Laser Powder Bed Fused 316L BT - effects of interlayer time and scanning velocity JF - Advanced engineering materials N2 - The control of residual stress (RS) remains a challenge in the manufacturing of metallic parts using the laser powder bed fusion process (LPBF). This layer-by-layer manufacturing approach gives rise to complex triaxial RS distributions, which require extensive characterization effort for a broader acceptance of LPBF in industry. This study focuses on the distribution of bulk triaxial RS and surface RS in LPBF austenitic steel 316L. The RS are determined by X-ray and neutron diffraction to characterize the RS distribution. Variations in the LPBF parameters interlayer time (ILT) and scanning velocity and their influence on the temperature distribution and resulting RS is investigated using thermographic data from in situ process monitoring. The RS in the LPBF 316L is tensile at the surface and compressive in the bulk. The RS is directly related to the thermal history of the part as shown by the in situ thermography data. Shorter ILT leads to higher temperatures of the part during the manufacturing, which decrease the RS and RS formation mechanisms. Interestingly, the surface RS does not agree with this observation. This study highlights the benefit of using multiple RS determination methods and in situ thermography monitoring to characterize the RS in LPBF processed parts. KW - in situ thermography KW - interlayer time KW - laser powder bed fusions KW - triaxial residual stresses KW - X-ray and neutron diffractions Y1 - 2021 U6 - https://doi.org/10.1002/adem.202101330 SN - 1438-1656 SN - 1527-2648 VL - 24 IS - 6 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kuhla, Kilian A1 - Willner, Sven N. A1 - Otto, Christian A1 - Geiger, Tobias A1 - Levermann, Anders T1 - Ripple resonance amplifies economic welfare loss from weather extremes JF - Environmental research letters : ERL / Institute of Physics N2 - The most complex but potentially most severe impacts of climate change are caused by extreme weather events. In a globally connected economy, damages can cause remote perturbations and cascading consequences-a ripple effect along supply chains. Here we show an economic ripple resonance that amplifies losses when consecutive or overlapping weather extremes and their repercussions interact. This amounts to an average amplification of 21% for climate-induced heat stress, river floods, and tropical cyclones. Modeling the temporal evolution of 1.8 million trade relations between >7000 regional economic sectors, we find that the regional responses to future extremes are strongly heterogeneous also in their resonance behavior. The induced effect on welfare varies between gains due to increased demand in some regions and losses due to demand or supply shortages in others. Within the current global supply network, the ripple resonance effect of extreme weather is strongest in high-income economies-an important effect to consider when evaluating past and future economic climate impacts. KW - consecutive disasters KW - economic ripple resonance KW - repercussion resonance KW - weather extremes KW - supply network KW - climate impacts KW - climate change Y1 - 2021 U6 - https://doi.org/10.1088/1748-9326/ac2932 SN - 1748-9326 VL - 16 IS - 11 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Sorgenfrei, Nomi A1 - Giangrisostomi, Erika A1 - Jay, Raphael Martin A1 - Kühn, Danilo A1 - Neppl, Stefan A1 - Ovsyannikov, Ruslan A1 - Sezen, Hikmet A1 - Svensson, Svante A1 - Föhlisch, Alexander T1 - Photodriven transient picosecond top-layer semiconductor to metal phase-transition in p-doped molybdenum disulfide JF - Advanced materials N2 - Visible light is shown to create a transient metallic S-Mo-S surface layer on bulk semiconducting p-doped indirect-bandgap 2H-MoS2. Optically created electron-hole pairs separate in the surface band bending region of the p-doped semiconducting crystal causing a transient accumulation of electrons in the surface region. This triggers a reversible 2H-semiconductor to 1T-metal phase-transition of the surface layer. Electron-phonon coupling of the indirect-bandgap p-doped 2H-MoS2 enables this efficient pathway even at a low density of excited electrons with a distinct optical excitation threshold and saturation behavior. This mechanism needs to be taken into consideration when describing the surface properties of illuminated p-doped 2H-MoS2. In particular, light-induced increased charge mobility and surface activation can cause and enhance the photocatalytic and photoassisted electrochemical hydrogen evolution reaction of water on 2H-MoS2. Generally, it opens up for a way to control not only the surface of p-doped 2H-MoS2 but also related dichalcogenides and layered systems. The findings are based on the sensitivity of time-resolved electron spectroscopy for chemical analysis with photon-energy-tuneable synchrotron radiation. KW - catalysis KW - dichalcogenides KW - hydrogen evolution reaction KW - phase transitions KW - photoelectron spectroscopy Y1 - 2021 U6 - https://doi.org/10.1002/adma.202006957 SN - 0935-9648 SN - 1521-4095 VL - 33 IS - 14 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Tait, Claudia E. A1 - Reckwitz, Anna A1 - Arvind, Malavika A1 - Neher, Dieter A1 - Bittl, Robert A1 - Behrends, Jan T1 - Spin-spin interactions and spin delocalisation in a doped organic semiconductor probed by EPR spectroscopy JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - The enhancement and control of the electrical conductivity of organic semiconductors is fundamental for their use in optoelectronic applications and can be achieved by molecular doping, which introduces additional charge carriers through electron transfer between a dopant molecule and the organic semiconductor. Here, we use Electron Paramagnetic Resonance (EPR) spectroscopy to characterise the unpaired spins associated with the charges generated by molecular doping of the prototypical organic semiconductor poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) and tris(pentafluorophenyl)borane (BCF). The EPR results reveal the P3HT radical cation as the only paramagnetic species in BCF-doped P3HT films and show evidence for increased mobility of the detected spins at high doping concentrations as well as formation of antiferromagnetically coupled spin pairs leading to decreased spin concentrations at low temperatures. The EPR signature for F(4)TCNQ-doped P3HT is found to be determined by spin exchange between P3HT radical cations and F(4)TCNQ radical anions. Results from continuous-wave and pulse EPR measurements suggest the presence of the unpaired spin on P3HT in a multitude of environments, ranging from free P3HT radical cations with similar properties to those observed in BCF-doped P3HT, to pairs of dipolar and exchange-coupled spins on P3HT and the dopant anion. Characterisation of the proton hyperfine interactions by ENDOR allowed quantification of the extent of spin delocalisation and revealed reduced delocalisation in the F(4)TCNQ-doped P3HT films. Y1 - 2021 U6 - https://doi.org/10.1039/d1cp02133h SN - 1463-9076 SN - 1463-9084 VL - 23 IS - 25 SP - 13827 EP - 13841 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Sandev, Trifce A1 - Domazetoski, Viktor A1 - Kocarev, Ljupco A1 - Metzler, Ralf A1 - Chechkin, Aleksei T1 - Heterogeneous diffusion with stochastic resetting JF - Journal of physics : A, Mathematical and theoretical N2 - We study a heterogeneous diffusion process (HDP) with position-dependent diffusion coefficient and Poissonian stochastic resetting. We find exact results for the mean squared displacement and the probability density function. The nonequilibrium steady state reached in the long time limit is studied. We also analyse the transition to the non-equilibrium steady state by finding the large deviation function. We found that similarly to the case of the normal diffusion process where the diffusion length grows like t (1/2) while the length scale xi(t) of the inner core region of the nonequilibrium steady state grows linearly with time t, in the HDP with diffusion length increasing like t ( p/2) the length scale xi(t) grows like t ( p ). The obtained results are verified by numerical solutions of the corresponding Langevin equation. KW - heterogeneous diffusion KW - Fokker-Planck equation KW - Langevin equation KW - stochastic resetting KW - nonequilibrium stationary state KW - large deviation function Y1 - 2022 U6 - https://doi.org/10.1088/1751-8121/ac491c SN - 1751-8113 SN - 1751-8121 VL - 55 IS - 7 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Sharma, Anjali A1 - Bekir, Marek A1 - Lomadze, Nino A1 - Jung, Se-Hyeong A1 - Pich, Andrij A1 - Santer, Svetlana T1 - Generation of local diffusioosmotic flow by light responsive microgels JF - Langmuir N2 - Here we show that microgels trapped at a solid wall can issue liquid flow and transport over distances several times larger than the particle size. The microgel consists of cross-linked poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AA) polymer chains loaded with cationic azobenzene-containing surfactant, which can assume either a trans-or a cis-state depending on the wavelength of the applied irradiation. The microgel, being a selective absorber of trans-isomers, responds by changing its volume under irradiation with light of appropriate wavelength at which the cis-isomers of the surfactant molecules diffuse out of the particle interior. Together with the change in particle size, the expelled cis-isomers form an excess of the concentration and subsequent gradient in osmotic pressure generating a halo of local light-driven diffusioosmotic (l-LDDO) flow. The direction and the strength of the l-LDDO depends on the intensity and irradiation wavelength, as well as on the amount of surfactant absorbed by the microgel. The flow pattern around a microgel is directed radially outward and can be maintained quasi-indefinitely under exposure to blue light when the trans-/cis-ratio is 2/1, establishing a photostationary state. Irradiation with UV light, on the other hand, generates a radially transient flow pattern, which inverts from inward to outward over time at low intensities. By measuring the displacement of tracer particles around neutral microgels during a temperature-induced collapse, we can exclude that a change in particle shape itself causes the flow, i.e., just by expulsion or uptake of water. Ultimately, it is its ability to selectively absorb two isomers of photosensitive surfactant under different irradiation conditions that leads to an effective pumping caused by a self-induced diffusioosmotic flow. Y1 - 2022 U6 - https://doi.org/10.1021/acs.langmuir.2c00259 SN - 0743-7463 SN - 1520-5827 VL - 38 IS - 20 SP - 6343 EP - 6351 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Eckert, Sebastian A1 - Vaz da Cruz, Vinícius A1 - Ochmann, Miguel A1 - Ahnen, Inga von A1 - Föhlisch, Alexander A1 - Huse, Nils T1 - Breaking the symmetry of pyrimidine BT - solvent effects and core-excited state dynamics JF - The journal of physical chemistry letters N2 - Symmetry and its breaking crucially define the chemical properties of molecules and their functionality. Resonant inelastic X-ray scattering is a local electronic structure probe reporting on molecular symmetry and its dynamical breaking within the femtosecond scattering duration. Here, we study pyrimidine, a system from the C-2v point group, in an aqueous solution environment, using scattering though its 2a(2) resonance. Despite the absence of clean parity selection rules for decay transitions from in-plane orbitals, scattering channels including decay from the 7b(2) and 11a(1) orbitals with nitrogen lone pair character are a direct probe for molecular symmetry. Computed spectra of explicitly solvated molecules sampled from a molecular dynamics simulation are combined with the results of a quantum dynamical description of the X-ray scattering process. We observe dominant signatures of core-excited Jahn-Teller induced symmetry breaking for resonant excitation. Solvent contributions are separable by shortening of the effective scattering duration through excitation energy detuning. Y1 - 2021 U6 - https://doi.org/10.1021/acs.jpclett.1c01865 SN - 1948-7185 VL - 12 IS - 35 SP - 8637 EP - 8643 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Klose, Ann Kristin A1 - Wunderling, Nico A1 - Winkelmann, Ricarda A1 - Donges, Jonathan T1 - What do we mean, 'tipping cascade'? JF - Environmental research letters : ERL N2 - Based on suggested interactions of potential tipping elements in the Earth's climate and in ecological systems, tipping cascades as possible dynamics are increasingly discussed and studied. The activation of such tipping cascades would impose a considerable risk for human societies and biosphere integrity. However, there are ambiguities in the description of tipping cascades within the literature so far. Here we illustrate how different patterns of multiple tipping dynamics emerge from a very simple coupling of two previously studied idealized tipping elements. In particular, we distinguish between a two phase cascade, a domino cascade and a joint cascade. A mitigation of an unfolding two phase cascade may be possible and common early warning indicators are sensitive to upcoming critical transitions to a certain degree. In contrast, a domino cascade may hardly be stopped once initiated and critical slowing down-based indicators fail to indicate tipping of the following element. These different potentials for intervention and anticipation across the distinct patterns of multiple tipping dynamics should be seen as a call to be more precise in future analyses of cascading dynamics arising from tipping element interactions in the Earth system. KW - tipping cascade KW - domino effect KW - tipping interactions KW - cascading regime KW - shifts KW - early warning indicators Y1 - 2021 U6 - https://doi.org/10.1088/1748-9326/ac3955 SN - 1748-9326 VL - 16 IS - 12 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Maiti, Snehanshu A1 - Makwana, Kirit A1 - Zhang, Heshou A1 - Yan, Huirong T1 - Cosmic-ray transport in magnetohydrodynamic turbulence JF - The astrophysical journal : an international review of spectroscopy and astronomical physics / part 1 N2 - This paper studies cosmic-ray (CR) transport in magnetohydrodynamic (MHD) turbulence. CR transport is strongly dependent on the properties of the magnetic turbulence. We perform test particle simulations to study the interactions of CR with both total MHD turbulence and decomposed MHD modes. The spatial diffusion coefficients and the pitch angle scattering diffusion coefficients are calculated from the test particle trajectories in turbulence. Our results confirm that the fast modes dominate the CR propagation, whereas Alfven and slow modes are much less efficient and have shown similar pitch-angle scattering rates. We investigate the cross field transport on large and small scales. On large/global scales, normal diffusion is observed and the diffusion coefficient is suppressed by M-A(zeta) compared to the parallel diffusion coefficients, with zeta closer to 4 in Alfven modes than that in total turbulence, as theoretically expected. For the CR transport on scales smaller than the turbulence injection scale, both the local and global magnetic reference frames are adopted. Superdiffusion is observed on such small scales in all the cases. Particularly, CR transport in Alfven modes show clear Richardson diffusion in the local reference frame. The diffusion transitions smoothly from the Richardson's one with index 1.5 to normal diffusion as the particle mean free path decreases from lambda(parallel to) >> L to lambda(parallel to) << L, where L is the injection/coherence length of turbulence. Our results have broad applications to CRs in various astrophysical environments. Y1 - 2022 U6 - https://doi.org/10.3847/1538-4357/ac46c8 SN - 1538-4357 VL - 926 IS - 1 PB - Institute of Physics Publ. CY - London ER - TY - JOUR A1 - Aranson, Igor S. A1 - Pikovskij, Arkadij T1 - Confinement and collective escape of active particles JF - Physical review letters N2 - Active matter broadly covers the dynamics of self-propelled particles. While the onset of collective behavior in homogenous active systems is relatively well understood, the effect of inhomogeneities such as obstacles and traps lacks overall clarity. Here, we study how interacting, self-propelled particles become trapped and released from a trap. We have found that captured particles aggregate into an orbiting condensate with a crystalline structure. As more particles are added, the trapped condensates escape as a whole. Our results shed light on the effects of confinement and quenched disorder in active matter. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevLett.128.108001 SN - 0031-9007 SN - 1079-7114 SN - 1092-0145 VL - 128 IS - 10 PB - American Physical Society CY - College Park, Md. ER - TY - JOUR A1 - Nakoudi, Konstantina A1 - Ritter, Christoph A1 - Stachlewska, Iwona Sylwia T1 - Properties of cirrus clouds over the European Arctic (Ny-Alesund, Svalbard) JF - Remote sensing / Molecular Diversity Preservation International (MDPI) N2 - Cirrus is the only cloud type capable of inducing daytime cooling or heating at the top of the atmosphere (TOA) and the sign of its radiative effect highly depends on its optical depth. However, the investigation of its geometrical and optical properties over the Arctic is limited. In this work the long-term properties of cirrus clouds are explored for the first time over an Arctic site (Ny-Alesund, Svalbard) using lidar and radiosonde measurements from 2011 to 2020. The optical properties were quality assured, taking into account the effects of specular reflections and multiple-scattering. Cirrus clouds were generally associated with colder and calmer wind conditions compared to the 2011-2020 climatology. However, the dependence of cirrus properties on temperature and wind speed was not strong. Even though the seasonal cycle was not pronounced, the winter-time cirrus appeared under lower temperatures and stronger wind conditions. Moreover, in winter, geometrically- and optically-thicker cirrus were found and their ice particles tended to be more spherical. The majority of cirrus was associated with westerly flow and westerly cirrus tended to be geometrically-thicker. Overall, optically-thinner layers tended to comprise smaller and less spherical ice crystals, most likely due to reduced water vapor deposition on the particle surface. Compared to lower latitudes, the cirrus layers over Ny-Alesund were more absorbing in the visible spectral region and they consisted of more spherical ice particles. KW - Arctic clouds KW - cirrus clouds KW - ice clouds KW - lidar Y1 - 2021 U6 - https://doi.org/10.3390/rs13224555 SN - 2072-4292 VL - 13 IS - 22 PB - MDPI CY - Basel ER - TY - JOUR A1 - Tönjes, Ralf A1 - Fiore, Carlos E. A1 - Pereira da Silva, Tiago T1 - Coherence resonance in influencer networks JF - Nature Communications N2 - Complex networks are abundant in nature and many share an important structural property: they contain a few nodes that are abnormally highly connected (hubs). Some of these hubs are called influencers because they couple strongly to the network and play fundamental dynamical and structural roles. Strikingly, despite the abundance of networks with influencers, little is known about their response to stochastic forcing. Here, for oscillatory dynamics on influencer networks, we show that subjecting influencers to an optimal intensity of noise can result in enhanced network synchronization. This new network dynamical effect, which we call coherence resonance in influencer networks, emerges from a synergy between network structure and stochasticity and is highly nonlinear, vanishing when the noise is too weak or too strong. Our results reveal that the influencer backbone can sharply increase the dynamical response in complex systems of coupled oscillators. Influencer networks include a small set of highly-connected nodes and can reach synchrony only via strong node interaction. Tonjes et al. show that introducing an optimal amount of noise enhances synchronization of such networks, which may be relevant for neuroscience or opinion dynamics applications. Y1 - 2021 U6 - https://doi.org/10.1038/s41467-020-20441-4 SN - 2041-1723 VL - 12 IS - 1 PB - Nature Publishing Group UK CY - London ER - TY - JOUR A1 - Becker, George D. A1 - D'Aloisio, Anson A1 - Christenson, Holly M. A1 - Zhu, Yongda A1 - Worseck, Gábor A1 - Bolton, James S. T1 - The mean free path of ionizing photons at 5 < z < 6 BT - evidence for rapid evolution near reionization JF - Monthly notices of the Royal Astronomical Society N2 - The mean free path of ionizing photons, lambda(mfp), is a key factor in the photoionization of the intergalactic medium (IGM). At z greater than or similar to 5, however, lambda(mfp) may be short enough that measurements towards QSOs are biased by the QSO proximity effect. We present new direct measurements of lambda(mfp) that address this bias and extend up to z similar to 6 for the first time. Our measurements at z similar to 5 are based on data from the Giant Gemini GMOS survey and new Keck LRIS observations of low-luminosity QSOs. At z similar to 6 we use QSO spectra from Keck ESI and VLT X-Shooter. We measure lambda(mfp) = 9.09(-1.28)(+1.62) proper Mpc and 0.75(-0.45)(+0.65) proper Mpc (68 percent confidence) at z = 5.1 and 6.0, respectively. The results at z = 5.1 are consistent with existing measurements, suggesting that bias from the proximity effect is minor at this redshift. At z = 6.0, however, we find that neglecting the proximity effect biases the result high by a factor of two or more. Our measurement at z = 6.0 falls well below extrapolations from lower redshifts, indicating rapid evolution in lambda(mfp) over 5 < z < 6. This evolution disfavours models in which reionization ended early enough that the IGM had time to fully relax hydrodynamically by z = 6, but is qualitatively consistent with models wherein reionization completed at z = 6 or even significantly later. Our mean free path results are most consistent with late reionization models wherein the IGM is still 20 percent neutral at z = 6, although our measurement at z = 6.0 is even lower than these models prefer. KW - intergalactic medium KW - quasars: absorption lines KW - cosmology: observations KW - dark ages KW - large-scale structure of Universe KW - reionization KW - first stars Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab2696 SN - 0035-8711 SN - 1365-2966 VL - 508 IS - 2 SP - 1853 EP - 1869 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Zu, Fengshuo A1 - Warby, Jonathan A1 - Stolterfoht, Martin A1 - Li, Jinzhao A1 - Shin, Dongguen A1 - Unger, Eva A1 - Koch, Norbert T1 - Photoinduced energy-level realignment at interfaces between organic semiconductors and metal-halide perovskites JF - Physical review letters N2 - In contrast to the common conception that the interfacial energy-level alignment is affixed once the interface is formed, we demonstrate that heterojunctions between organic semiconductors and metal-halide perovskites exhibit huge energy-level realignment during photoexcitation. Importantly, the photoinduced level shifts occur in the organic component, including the first molecular layer in direct contact with the perovskite. This is caused by charge-carrier accumulation within the organic semiconductor under illumination and the weak electronic coupling between the junction components. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevLett.127.246401 SN - 0031-9007 SN - 1079-7114 VL - 127 IS - 24 PB - American Physical Society CY - College Park ER - TY - THES A1 - Ronneberger, Sebastian T1 - Nanolayer Fused Deposition Modeling (NanoFDM) BT - from 2D information labels to 4D printing Y1 - 2024 ER - TY - JOUR A1 - Zeitz, Maria A1 - Reese, Ronja A1 - Beckmann, Johanna A1 - Krebs-Kanzow, Uta A1 - Winkelmann, Ricarda T1 - Impact of the melt-albedo feedback on the future evolution of the Greenland Ice Sheet with PISM-dEBM-simple JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Surface melting of the Greenland Ice Sheet contributes a large amount to current and future sea level rise. Increased surface melt may lower the reflectivity of the ice sheet surface and thereby increase melt rates: the so-called melt-albedo feedback describes this self-sustaining increase in surface melting. In order to test the effect of the melt-albedo feedback in a prognostic ice sheet model, we implement dEBM-simple, a simplified version of the diurnal Energy Balance Model dEBM, in the Parallel Ice Sheet Model (PISM). The implementation includes a simple representation of the melt-albedo feedback and can thereby replace the positive-degree-day melt scheme. Using PISM-dEBM-simple, we find that this feedback increases ice loss through surface warming by 60 % until 2300 for the high-emission scenario RCP8.5 when compared to a scenario in which the albedo remains constant at its present-day values. With an increase of 90 % compared to a fixed-albedo scenario, the effect is more pronounced for lower surface warming under RCP2.6. Furthermore, assuming an immediate darkening of the ice surface over all summer months, we estimate an upper bound for this effect to be 70 % in the RCP8.5 scenario and a more than 4-fold increase under RCP2.6. With dEBM-simple implemented in PISM, we find that the melt-albedo feedback is an essential contributor to mass loss in dynamic simulations of the Greenland Ice Sheet under future warming. Y1 - 2021 U6 - https://doi.org/10.5194/tc-15-5739-2021 SN - 1994-0416 SN - 1994-0424 VL - 15 IS - 12 SP - 5739 EP - 5764 PB - Copernicus CY - Katlenburg-Lindau ER - TY - THES A1 - Kanehira, Yuya T1 - Versatile DNA origami based SERS substrates for spectroscopic applications Y1 - 2023 ER - TY - JOUR A1 - Haas, Bernhard A1 - Shprits, Yuri Y. A1 - Allison, Hayley A1 - Wutzig, Michael A1 - Wang, Dedong T1 - Which parameter controls ring current electron dynamics JF - Frontiers in astronomy and space sciences N2 - Predicting the electron population of Earth's ring current during geomagnetic storms still remains a challenging task. In this work, we investigate the sensitivity of 10 keV ring current electrons to different driving processes, parameterised by the Kp index, during several moderate and intense storms. Results are validated against measurements from the Van Allen Probes satellites. Perturbing the Kp index allows us to identify the most dominant processes for moderate and intense storms respectively. We find that during moderate storms (Kp < 6) the drift velocities mostly control the behaviour of low energy electrons, while loss from wave-particle interactions is the most critical parameter for quantifying the evolution of intense storms (Kp > 6). Perturbations of the Kp index used to drive the boundary conditions at GEO and set the plasmapause location only show a minimal effect on simulation results over a limited L range. It is further shown that the flux at L & SIM; 3 is more sensitive to changes in the Kp index compared to higher L shells, making it a good proxy for validating the source-loss balance of a ring current model. KW - ring current KW - magnetosphere KW - electron lifetimes KW - electrons KW - van allen probes (RBSP) KW - ring current model KW - verb Y1 - 2022 U6 - https://doi.org/10.3389/fspas.2022.911002 SN - 2296-987X VL - 9 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Hindes, Jason A1 - Assaf, Michael A1 - Schwartz, Ira B. T1 - Outbreak size distribution in stochastic epidemic models JF - Physical review letters N2 - Motivated by recent epidemic outbreaks, including those of COVID-19, we solve the canonical problem of calculating the dynamics and likelihood of extensive outbreaks in a population within a large class of stochastic epidemic models with demographic noise, including the susceptible-infected-recovered (SIR) model and its general extensions. In the limit of large populations, we compute the probability distribution for all extensive outbreaks, including those that entail unusually large or small (extreme) proportions of the population infected. Our approach reveals that, unlike other well-known examples of rare events occurring in discrete-state stochastic systems, the statistics of extreme outbreaks emanate from a full continuum of Hamiltonian paths, each satisfying unique boundary conditions with a conserved probability flux. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevLett.128.078301 SN - 0031-9007 SN - 1079-7114 SN - 1092-0145 VL - 128 IS - 7 PB - American Physical Society CY - College Park, Md. ER - TY - JOUR A1 - Bozzo, Enrico A1 - Romano, Patrizia A1 - Ferrigno, Carlo A1 - Oskinova, Lida T1 - The symbiotic X-ray binaries Sct X-1, 4U 1700+24, and IGR J17329-2731 JF - Monthly notices of the Royal Astronomical Society N2 - Symbiotic X-ray binaries are systems hosting a neutron star accreting form the wind of a late-type companion. These are rare objects and so far only a handful of them are known. One of the most puzzling aspects of the symbiotic X-ray binaries is the possibility that they contain strongly magnetized neutron stars. These are expected to be evolutionary much younger compared to their evolved companions and could thus be formed through the (yet poorly known) accretion induced collapse of a white dwarf. In this paper, we perform a broad-band X-ray and soft gamma-ray spectroscopy of two known symbiotic binaries, Sct X-1 and 4U 1700+24, looking for the presence of cyclotron scattering features that could confirm the presence of strongly magnetized NSs. We exploited available Chandra, Swift, and NuSTAR data. We find no evidence of cyclotron resonant scattering features (CRSFs) in the case of Sct X-1 but in the case of 4U 1700+24 we suggest the presence of a possible CRSF at similar to 16 keV and its first harmonic at similar to 31 keV, although we could not exclude alternative spectral models for the broad-band fit. If confirmed by future observations, 4U 1700+24 could be the second symbiotic X-ray binary with a highly magnetized accretor. We also report about our long-term monitoring of the last discovered symbiotic X-ray binary IGR J17329-2731 performed with Swift/XRT. The monitoring revealed that, as predicted, in 2017 this object became a persistent and variable source, showing X-ray flares lasting for a few days and intriguing obscuration events that are interpreted in the context of clumpy wind accretion. KW - accretion KW - accretion discs KW - stars: massive KW - stars: neutron KW - X-rays: binaries KW - X-rays: individual: SctX-1 KW - X-rays: individual: 4U1700+24; KW - X-rays: stars KW - X-rays: individual: IGRJ17329-2731 Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac907 SN - 0035-8711 SN - 1365-2966 VL - 513 IS - 1 SP - 42 EP - 54 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Perdigón-Toro, Lorena A1 - Le Quang Phuong, A1 - Zeiske, Stefan A1 - Vandewal, Koen A1 - Armin, Ardalan A1 - Shoaee, Safa A1 - Neher, Dieter T1 - Excitons dominate the emission from PM6 BT - Y6 solar cells, but this does not help the open-circuit voltage of the device JF - ACS energy letters / American Chemical Society N2 - Non-fullerene acceptors (NFAs) are far more emissive than their fullerene-based counterparts. Here, we study the spectral properties of photocurrent generation and recombination of the blend of the donor polymer PM6 with the NFA Y6. We find that the radiative recombination of free charges is almost entirely due to the re-occupation and decay of Y6 singlet excitons, but that this pathway contributes less than 1% to the total recombination. As such, the open-circuit voltage of the PM6:Y6 blend is determined by the energetics and kinetics of the charge-transfer (CT) state. Moreover, we find that no information on the energetics of the CT state manifold can be gained from the low-energy tail of the photovoltaic external quantum efficiency spectrum, which is dominated by the excitation spectrum of the Y6 exciton. We, finally, estimate the charge-separated state to lie only 120 meV below the Y6 singlet exciton energy, meaning that this blend indeed represents a high-efficiency system with a low energetic offset. Y1 - 2021 U6 - https://doi.org/10.1021/acsenergylett.0c02572 SN - 2380-8195 VL - 6 IS - 2 SP - 557 EP - 564 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Chaurasia, Swami Vivekanandji A1 - Dietrich, Tim A1 - Rosswog, Stephan T1 - Black hole-neutron star simulations with the BAM code BT - first tests and simulations JF - Physical review : D, Particles, fields, gravitation, and cosmology N2 - The first detections of black hole-neutron star mergers (GW200105 and GW200115) by the LIGO-Virgo-Kagra Collaboration mark a significant scientific breakthrough. The physical interpretation of pre- and postmerger signals requires careful cross-examination between observational and theoretical modelling results. Here we present the first set of black hole-neutron star simulations that were obtained with the numerical-relativity code BAM. Our initial data are constructed using the public LORENE spectral library, which employs an excision of the black hole interior. BAM, in contrast, uses the moving-puncture gauge for the evolution. Therefore, we need to "stuff" the black hole interior with smooth initial data to evolve the binary system in time. This procedure introduces constraint violations such that the constraint damping properties of the evolution system are essential to increase the accuracy of the simulation and in particular to reduce spurious center-of-mass drifts. Within BAM we evolve the Z4c equations and we compare our gravitational-wave results with those of the SXS collaboration and results obtained with the SACRA code. While we find generally good agreement with the reference solutions and phase differences less than or similar to 0.5 rad at the moment of merger, the absence of a clean convergence order in our simulations does not allow for a proper error quantification. We finally present a set of different initial conditions to explore how the merger of black hole neutron star systems depends on the involved masses, spins, and equations of state. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevD.104.084010 SN - 2470-0010 SN - 2470-0029 VL - 104 IS - 8 PB - American Physical Society CY - Ridge, NY ER - TY - JOUR A1 - Oskinova, Lida A1 - Schaerer, Daniel T1 - Ionization of He II in star-forming galaxies by X-rays from cluster winds and superbubbles JF - Astronomy and astrophysics : an international weekly journal N2 - The nature of the sources powering nebular He II emission in star-forming galaxies remains debated, and various types of objects have been considered, including Wolf-Rayet stars, X-ray binaries, and Population III stars. Modern X-ray observations show the ubiquitous presence of hot gas filling star-forming galaxies. We use a collisional ionization plasma code to compute the specific He II ionizing flux produced by hot gas and show that if its temperature is not too high (less than or similar to 2.5 MK), then the observed levels of soft diffuse X-ray radiation could explain He II ionization in galaxies. To gain a physical understanding of this result, we propose a model that combines the hydrodynamics of cluster winds and hot superbubbles with observed populations of young massive clusters in galaxies. We find that in low-metallicity galaxies, the temperature of hot gas is lower and the production rate of He II ionizing photons is higher compared to high-metallicity galaxies. The reason is that the slower stellar winds of massive stars in lower-metallicity galaxies input less mechanical energy in the ambient medium. Furthermore, we show that ensembles of star clusters up to similar to 10-20 Myr old in galaxies can produce enough soft X-rays to induce nebular He II emission. We discuss observations of the template low-metallicity galaxy I Zw 18 and suggest that the He II nebula in this galaxy is powered by a hot superbubble. Finally, appreciating the complex nature of stellar feedback, we suggest that soft X-rays from hot superbubbles are among the dominant sources of He II ionizing flux in low-metallicity star-forming galaxies. KW - galaxies KW - ISM KW - high-redshift KW - bubbles KW - X-rays Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202142520 SN - 0004-6361 SN - 1432-0746 VL - 661 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Barra, Felipe A1 - Hovhannisyan, Karen A1 - Imparato, Alberto T1 - Quantum batteries at the verge of a phase transition JF - New journal of physics : the open-access journal for physics N2 - Starting from the observation that the reduced state of a system strongly coupled to a bath is, in general, an athermal state, we introduce and study a cyclic battery-charger quantum device that is in thermal equilibrium, or in a ground state, during the charge storing stage. The cycle has four stages: the equilibrium storage stage is interrupted by disconnecting the battery from the charger, then work is extracted from the battery, and then the battery is reconnected with the charger; finally, the system is brought back to equilibrium. At no point during the cycle are the battery-charger correlations artificially erased. We study the case where the battery and charger together comprise a spin-1/2 Ising chain, and show that the main characteristics-the extracted energy and the thermodynamic efficiency-can be enhanced by operating the cycle close to the quantum phase transition point. When the battery is just a single spin, we find that the output work and efficiency show a scaling behavior at criticality and derive the corresponding critical exponents. Due to always present correlations between the battery and the charger, operations that are equivalent from the perspective of the battery can entail different energetic costs for switching the battery-charger coupling. This happens only when the coupling term does not commute with the battery's bare Hamiltonian, and we use this purely quantum leverage to further optimize the performance of the device. KW - quantum batteries KW - quantum thermodynamics KW - quantum phase transition Y1 - 2022 U6 - https://doi.org/10.1088/1367-2630/ac43ed SN - 1367-2630 VL - 24 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Pauzon, Camille A1 - Mishurova, Tatiana A1 - Evsevleev, Sergei A1 - Dubiez-Le Goff, Sophie A1 - Murugesan, Saravanakumar A1 - Bruno, Giovanni A1 - Hryha, Eduard T1 - Residual stresses and porosity in Ti-6Al-4V produced by laser powder bed fusion as a function of process atmosphere and component design JF - Additive manufacturing N2 - The influence of the process gas, laser scan speed, and sample thickness on the build-up of residual stresses and porosity in Ti-6Al-4V produced by laser powder bed fusion was studied. Pure argon and helium, as well as a mixture of those (30% helium), were employed to establish process atmospheres with a low residual oxygen content of 100 ppm O-2. The results highlight that the subsurface residual stresses measured by X-ray diffraction were significantly lower in the thin samples (220 MPa) than in the cuboid samples (645 MPa). This difference was attributed to the shorter laser vector length, resulting in heat accumulation and thus in-situ stress relief. The addition of helium to the process gas did not introduce additional subsurface residual stresses in the simple geometries, even for the increased scanning speed. Finally, larger deflection was found in the cantilever built under helium (after removal from the baseplate), than in those produced under argon and an argon-helium mixture. This result demonstrates that complex designs involving large scanned areas could be subjected to higher residual stress when manufactured under helium due to the gas's high thermal conductivity, heat capacity, and thermal diffusivity. KW - Residual stresses KW - Laser powder bed fusion KW - Process atmosphere KW - Helium KW - Ti-6Al-4V Y1 - 2021 U6 - https://doi.org/10.1016/j.addma.2021.102340 SN - 2214-8604 VL - 47 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pranav, Manasi A1 - Benduhn, Johannes A1 - Nyman, Mathias A1 - Hosseini, Seyed Mehrdad A1 - Kublitski, Jonas A1 - Shoaee, Safa A1 - Neher, Dieter A1 - Leo, Karl A1 - Spoltore, Donato T1 - Enhanced charge selectivity via anodic-C60 layer reduces nonradiative losses in organic solar cells JF - ACS applied materials & interfaces N2 - Interfacial layers in conjunction with suitable charge-transport layers can significantly improve the performance of optoelectronic devices by facilitating efficient charge carrier injection and extraction. This work uses a neat C-60 interlayer on the anode to experimentally reveal that surface recombination is a significant contributor to nonradiative recombination losses in organic solar cells. These losses are shown to proportionally increase with the extent of contact between donor molecules in the photoactive layer and a molybdenum oxide (MoO3) hole extraction layer, proven by calculating voltage losses in low- and high-donor-content bulk heterojunction device architectures. Using a novel in-device determination of the built-in voltage, the suppression of surface recombination, due to the insertion of a thin anodic-C-60 interlayer on MoO3, is attributed to an enhanced built-in potential. The increased built-in voltage reduces the presence of minority charge carriers at the electrodes-a new perspective on the principle of selective charge extraction layers. The benefit to device efficiency is limited by a critical interlayer thickness, which depends on the donor material in bilayer devices. Given the high popularity of MoO3 as an efficient hole extraction and injection layer and the increasingly popular discussion on interfacial phenomena in organic optoelectronic devices, these findings are relevant to and address different branches of organic electronics, providing insights for future device design. KW - nonradiative losses KW - molybdenum oxide KW - organic solar cells KW - interfacial layers KW - charge selectivity Y1 - 2021 U6 - https://doi.org/10.1021/acsami.1c00049 SN - 1944-8244 SN - 1944-8252 VL - 13 IS - 10 SP - 12603 EP - 12609 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - He, Yushuang A1 - Wang, Feipeng A1 - He, Li A1 - Wang, Qiang A1 - Li, Jian A1 - Qian, Yihua A1 - Gerhard, Reimund A1 - Plath, Ronald T1 - An insight Into the role of Nano-Alumina on DC Flashover-Resistance and surface charge variation of Epoxy Nanocomposites JF - IEEE transactions on dielectrics and electrical insulation N2 - The addition of nano-Al2O3 has been shown to enhance the breakdown voltage of epoxy resin, but its flashover results appeared with disputation. This work concentrates on the surface charge variation and dc flashover performance of epoxy resin with nano-Al2O3 doping. The dispersion of nano-Al2O3 in epoxy is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The dc flashover voltages of samples under either positive or negative polarity are measured with a finger-electrode system, and the surface charge variations before and after flashovers were identified from the surface potential mapping. The results evidence that nano-Al2O3 would lead to a 16.9% voltage drop for the negative flashovers and a 6.8% drop for positive cases. It is found that one-time flashover clears most of the accumulated surface charges, regardless of positive or negative. As a result, the ground electrode is neighbored by an equipotential zone enclosed with low-density heterocharges. The equipotential zone tends to be broadened after 20 flashovers. The nano-Al2O3 is noticed as beneficial to downsize the equipotential zone due to its capability on charge migration, which is reasonable to maintain flashover voltage at a high level after multiple flashovers. Hence, nano-Al2O3 plays a significant role in improving epoxy with high resistance to multiple flashovers. KW - surface morphology KW - Epoxy resins KW - Electric potential KW - Surface treatment KW - Doping KW - Epoxy resin KW - multiple KW - flashover KW - nanocomposite KW - surface charge Y1 - 2022 U6 - https://doi.org/10.1109/TDEI.2022.3173510 SN - 1070-9878 SN - 1558-4135 VL - 29 IS - 3 SP - 1022 EP - 1029 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER - TY - JOUR A1 - Ochmann, Miguel A1 - Vaz da Cruz, Vinicius A1 - Eckert, Sebastian A1 - Huse, Nils A1 - Föhlisch, Alexander T1 - R-Group stabilization in methylated formamides observed by resonant inelastic X-ray scattering JF - Chemical communications: ChemComm N2 - The inherent stability of methylated formamides is traced to a stabilization of the deep-lying sigma-framework by resonant inelastic X-ray scattering at the nitrogen K-edge. Charge transfer from the amide nitrogen to the methyl groups underlie this stabilization mechanism that leaves the aldehyde group essentially unaltered and explains the stability of secondary and tertiary amides. Y1 - 2022 U6 - https://doi.org/10.1039/d2cc00053a SN - 1359-7345 SN - 1364-548X VL - 58 IS - 63 SP - 8834 EP - 8837 PB - The Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Culpan, Richard A1 - Geier, Stephan A1 - Reindl, Nicole A1 - Pelisoli, Ingrid A1 - Gentile Fusillo, Nicola Pietro A1 - Vorontseva, Alina T1 - The population of hot subdwarf stars studied with Gaia BT - IV. catalogues of hot subluminous stars based on Gaia EDR3 JF - Astronomy and astrophysics : an international weekly journal N2 - In light of substantial new discoveries of hot subdwarfs by ongoing spectroscopic surveys and the availability of the Gaia mission Early Data Release 3 (EDR3), we compiled new releases of two catalogues of hot subluminous stars: the data release 3 (DR3) catalogue of the known hot subdwarf stars contains 6616 unique sources and provides multi-band photometry, and astrometry from Gaia EDR3 as well as classifications based on spectroscopy and colours. This is an increase of 742 objects over the DR2 catalogue. This new catalogue provides atmospheric parameters for 3087 stars and radial velocities for 2791 stars from the literature. In addition, we have updated the Gaia Data Release 2 (DR2) catalogue of hot subluminous stars using the improved accuracy of the Gaia EDR3 data set together with updated quality and selection criteria to produce the Gaia EDR3 catalogue of 61 585 hot subluminous stars, representing an increase of 21 785 objects. The improvements in Gaia EDR3 astrometry and photometry compared to Gaia DR2 have enabled us to define more sophisticated selection functions. In particular, we improved hot subluminous star detection in the crowded regions of the Galactic plane as well as in the direction of the Magellanic Clouds by including sources with close apparent neighbours but with flux levels that dominate the neighbourhood. KW - subdwarfs KW - Hertzsprung-Russell and C-M diagrams KW - binaries: general KW - stars: horizontal-branch KW - catalogs Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202243337 SN - 1432-0746 VL - 662 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Rüdiger, Günther A1 - Schultz, Manfred A1 - Hollerbach, Rainer T1 - Destabilization of super-rotating Taylor-Couette flows by current-free helical magnetic fields JF - Journal of plasma physics N2 - In an earlier paper we showed that the combination of azimuthal magnetic fields and super-rotation in Taylor-Couette flows of conducting fluids can be unstable against non-axisymmetric perturbations if the magnetic Prandtl number of the fluid is Pm not equal 1. Here we demonstrate that the addition of a weak axial field component allows axisymmetric perturbation patterns for Pm of order unity depending on the boundary conditions. The axisymmetric modes only occur for magnetic Mach numbers (of the azimuthal field) of order unity, while higher values are necessary for the non-axisymmetric modes. The typical growth time of the instability and the characteristic time scale of the axial migration of the axisymmetric mode are long compared with the rotation period, but short compared with the magnetic diffusion time. The modes travel in the positive or negative z direction along the rotation axis depending on the sign of B phi Bz. We also demonstrate that the azimuthal components of flow and field perturbations travel in phase if vertical bar B phi vertical bar >> vertical bar B-z vertical bar, independent of the form of the rotation law. Within a short-wave approximation for thin gaps it is also shown (in an appendix) that for ideal fluids the considered helical magnetorotational instability only exists for rotation laws with negative shear. KW - plasma instabilities KW - astrophysical plasmas Y1 - 2021 U6 - https://doi.org/10.1017/S0022377821000295 SN - 1469-7807 VL - 87 IS - 2 PB - Cambridge University Press CY - London ER - TY - JOUR A1 - Feldmann, Johannes A1 - Reese, Ronja A1 - Winkelmann, Ricarda A1 - Levermann, Anders T1 - Shear-margin melting causes stronger transient ice discharge than ice-stream melting in idealized simulations JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Basal ice-shelf melting is the key driver of Antarctica's increasing sea-level contribution. In diminishing the buttressing force of the ice shelves that fringe the ice sheet, the melting increases the ice discharge into the ocean. Here we contrast the influence of basal melting in two different ice-shelf regions on the time-dependent response of an isothermal, inherently buttressed ice-sheet-shelf system. In the idealized numerical simulations, the basal-melt perturbations are applied close to the grounding line in the ice-shelf's (1) ice-stream region, where the ice shelf is fed by the fastest ice masses that stream through the upstream bed trough and (2) shear margins, where the ice flow is slower. The results show that melting below one or both of the shear margins can cause a decadal to centennial increase in ice discharge that is more than twice as large compared to a similar perturbation in the ice-stream region. We attribute this to the fact that melt-induced ice-shelf thinning in the central grounding-line region is attenuated very effectively by the fast flow of the central ice stream. In contrast, the much slower ice dynamics in the lateral shear margins of the ice shelf facilitate sustained ice-shelf thinning and thereby foster buttressing reduction. Regardless of the melt location, a higher melt concentration toward the grounding line generally goes along with a stronger response. Our results highlight the vulnerability of outlet glaciers to basal melting in stagnant, buttressing-relevant ice-shelf regions, a mechanism that may gain importance under future global warming. Y1 - 2022 U6 - https://doi.org/10.5194/tc-16-1927-2022 SN - 1994-0416 SN - 1994-0424 VL - 16 IS - 5 SP - 1927 EP - 1940 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Petreska, Irina A1 - Pejov, Ljupco A1 - Sandev, Trifce A1 - Kocarev, Ljupčo A1 - Metzler, Ralf T1 - Tuning of the dielectric relaxation and complex susceptibility in a system of polar molecules: a generalised model based on rotational diffusion with resetting JF - Fractal and fractional N2 - The application of the fractional calculus in the mathematical modelling of relaxation processes in complex heterogeneous media has attracted a considerable amount of interest lately. The reason for this is the successful implementation of fractional stochastic and kinetic equations in the studies of non-Debye relaxation. In this work, we consider the rotational diffusion equation with a generalised memory kernel in the context of dielectric relaxation processes in a medium composed of polar molecules. We give an overview of existing models on non-exponential relaxation and introduce an exponential resetting dynamic in the corresponding process. The autocorrelation function and complex susceptibility are analysed in detail. We show that stochastic resetting leads to a saturation of the autocorrelation function to a constant value, in contrast to the case without resetting, for which it decays to zero. The behaviour of the autocorrelation function, as well as the complex susceptibility in the presence of resetting, confirms that the dielectric relaxation dynamics can be tuned by an appropriate choice of the resetting rate. The presented results are general and flexible, and they will be of interest for the theoretical description of non-trivial relaxation dynamics in heterogeneous systems composed of polar molecules. KW - rotational diffusion KW - memory kernel KW - Fokker-Planck equation KW - non-exponential relaxation KW - autocorrelation function KW - complex KW - susceptibility Y1 - 2022 U6 - https://doi.org/10.3390/fractalfract6020088 SN - 2504-3110 VL - 6 IS - 2 PB - MDPI AG, Fractal Fract Editorial Office CY - Basel ER - TY - JOUR A1 - Zhao, Yuhang A1 - Sarhan, Radwan Mohamed A1 - Eljarrat, Alberto A1 - Kochovski, Zdravko A1 - Koch, Christoph A1 - Schmidt, Bernd A1 - Koopman, Wouter-Willem Adriaan A1 - Lu, Yan T1 - Surface-functionalized Au-Pd nanorods with enhanced photothermal conversion and catalytic performance JF - ACS applied materials & interfaces N2 - Bimetallic nanostructures comprising plasmonic and catalytic components have recently emerged as a promising approach to generate a new type of photo-enhanced nanoreactors. Most designs however concentrate on plasmon-induced charge separation, leaving photo-generated heat as a side product. This work presents a photoreactor based on Au-Pd nanorods with an optimized photothermal conversion, which aims to effectively utilize the photo-generated heat to increase the rate of Pd-catalyzed reactions. Dumbbell-shaped Au nanorods were fabricated via a seed-mediated growth method using binary surfactants. Pd clusters were selectively grown at the tips of the Au nanorods, using the zeta potential as a new synthetic parameter to indicate the surfactant remaining on the nanorod surface. The photothermal conversion of the Au-Pd nanorods was improved with a thin layer of polydopamine (PDA) or TiO2. As a result, a 60% higher temperature increment of the dispersion compared to that for bare Au rods at the same light intensity and particle density could be achieved. The catalytic performance of the coated particles was then tested using the reduction of 4-nitrophenol as the model reaction. Under light, the PDA-coated Au-Pd nanorods exhibited an improved catalytic activity, increasing the reaction rate by a factor 3. An analysis of the activation energy confirmed the photoheating effect to be the dominant mechanism accelerating the reaction. Thus, the increased photothermal heating is responsible for the reaction acceleration. Interestingly, the same analysis shows a roughly 10% higher reaction rate for particles under illumination compared to under dark heating, possibly implying a crucial role of localized heat gradients at the particle surface. Finally, the coating thickness was identified as an essential parameter determining the photothermal conversion efficiency and the reaction acceleration. KW - Au-Pd nanorods KW - PDA KW - photothermal conversion KW - surface plasmon KW - 4-nitrophenol Y1 - 2022 U6 - https://doi.org/10.1021/acsami.2c00221 SN - 1944-8244 SN - 1944-8252 VL - 14 IS - 15 SP - 17259 EP - 17272 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Hillwig, Todd C. A1 - Reindl, Nicole A1 - Rotter, Hannah M. A1 - Rengstorf, Adam W. A1 - Heber, Ulrich A1 - Irrgang, Andreas T1 - Two evolved close binary stars: GALEX J015054.4+310745 and the central star of the planetary nebula Hen 2-84 JF - Monthly notices of the Royal Astronomical Society N2 - As part of a survey to find close binary systems among central stars of planetary nebula, we present two newly discovered binary systems. GALEX J015054.4+310745 is identified as the central star of the possible planetary nebula Fr 2-22. We find it to be a single-lined spectroscopic binary with an orbital period of 0.2554435(10) d. We support the previous identification of GALEX J015054.4+310745 as an sdB star and provide physical parameters for the star from spectral modelling. We identify its undetected companion as a likely He white dwarf. Based on this information, we find it unlikely that Fr 2-22 is a true planetary nebula. In addition, the central star of the true planetary nebula Hen 2-84 is found to be a photometric variable, likely due to the irradiation of a cool companion. The system has an orbital period of 0.485645(30) d. We discuss limits on binary parameters based on the available light-curve data. Hen 2-84 is a strongly shaped bipolar planetary nebula, which we now add to the growing list of axially or point-symmetric planetary nebulae with a close binary central star. KW - binaries: close KW - stars: individual: GALEX J015054.4+310745 KW - subdwarfs KW - planetary nebulae: individual: Hen 2-84 Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac226 SN - 0035-8711 SN - 1365-2966 VL - 511 IS - 2 SP - 2033 EP - 2039 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Zeitz, Maria A1 - Haacker, Jan M. A1 - Donges, Jonathan F. A1 - Albrecht, Torsten A1 - Winkelmann, Ricarda T1 - Dynamic regimes of the Greenland Ice Sheet emerging from interacting melt-elevation and glacial isostatic adjustment feedbacks JF - Earth system dynamics N2 - The stability of the Greenland Ice Sheet under global warming is governed by a number of dynamic processes and interacting feedback mechanisms in the ice sheet, atmosphere and solid Earth. Here we study the long-term effects due to the interplay of the competing melt-elevation and glacial isostatic adjustment (GIA) feedbacks for different temperature step forcing experiments with a coupled ice-sheet and solid-Earth model. Our model results show that for warming levels above 2 degrees C, Greenland could become essentially ice-free within several millennia, mainly as a result of surface melting and acceleration of ice flow. These ice losses are mitigated, however, in some cases with strong GIA feedback even promoting an incomplete recovery of the Greenland ice volume. We further explore the full-factorial parameter space determining the relative strengths of the two feedbacks: our findings suggest distinct dynamic regimes of the Greenland Ice Sheets on the route to destabilization under global warming - from incomplete recovery, via quasi-periodic oscillations in ice volume to ice-sheet collapse. In the incomplete recovery regime, the initial ice loss due to warming is essentially reversed within 50 000 years, and the ice volume stabilizes at 61 %-93 % of the present-day volume. For certain combinations of temperature increase, atmospheric lapse rate and mantle viscosity, the interaction of the GIA feedback and the melt-elevation feedback leads to self-sustained, long-term oscillations in ice-sheet volume with oscillation periods between 74 000 and over 300 000 years and oscillation amplitudes between 15 %-70 % of present-day ice volume. This oscillatory regime reveals a possible mode of internal climatic variability in the Earth system on timescales on the order of 100 000 years that may be excited by or synchronized with orbital forcing or interact with glacial cycles and other slow modes of variability. Our findings are not meant as scenario-based near-term projections of ice losses but rather providing insight into of the feedback loops governing the "deep future" and, thus, long-term resilience of the Greenland Ice Sheet. Y1 - 2022 U6 - https://doi.org/10.5194/esd-13-1077-2022 SN - 2190-4979 SN - 2190-4987 VL - 13 IS - 3 SP - 1077 EP - 1096 PB - Copernicus Publ. CY - Göttingen ER - TY - JOUR A1 - Thapa, Samudrajit A1 - Park, Seongyu A1 - Kim, Yeongjin A1 - Jeon, Jae-Hyung A1 - Metzler, Ralf A1 - Lomholt, Michael A. T1 - Bayesian inference of scaled versus fractional Brownian motion JF - Journal of physics : A, mathematical and theoretical N2 - We present a Bayesian inference scheme for scaled Brownian motion, and investigate its performance on synthetic data for parameter estimation and model selection in a combined inference with fractional Brownian motion. We include the possibility of measurement noise in both models. We find that for trajectories of a few hundred time points the procedure is able to resolve well the true model and parameters. Using the prior of the synthetic data generation process also for the inference, the approach is optimal based on decision theory. We include a comparison with inference using a prior different from the data generating one. KW - Bayesian inference KW - scaled Brownian motion KW - single particle tracking Y1 - 2022 U6 - https://doi.org/10.1088/1751-8121/ac60e7 SN - 1751-8113 SN - 1751-8121 VL - 55 IS - 19 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Varykhalov, Andrei A1 - Freyse, Friedrich A1 - Aguilera, Irene A1 - Battiato, Marco A1 - Krivenkov, Maxim A1 - Marchenko, Dmitry A1 - Bihlmayer, Gustav A1 - Blugel, Stefan A1 - Rader, Oliver A1 - Sanchez-Barriga, Jaime T1 - Effective mass enhancement and ultrafast electron dynamics of Au(111) surface state coupled to a quantum well JF - Physical Review Research N2 - We show that, although the equilibrium band dispersion of the Shockley-type surface state of two-dimensional Au(111) quantum films grown on W(110) does not deviate from the expected free-electron-like behavior, its nonequilibrium energy-momentum dispersion probed by time- and angle-resolved photoemission exhibits a remarkable kink above the Fermi level due to a significant enhancement of the effective mass. The kink is pronounced for certain thicknesses of the Au quantum well and vanishes in the very thin limit. We identify the kink as induced by the coupling between the Au(111) surface state and emergent quantum-well states which probe directly the buried gold-tungsten interface. The signatures of the coupling are further revealed by our time-resolved measurements which show that surface state and quantum-well states thermalize together behaving as dynamically locked electron populations. In particular, relaxation of hot carriers following laser excitation is similar for both surface state and quantum-well states and much slower than expected for a bulk metallic system. The influence of quantum confinement on the interplay between elementary scattering processes of the electrons at the surface and ultrafast carrier transport in the direction perpendicular to the surface is shown to be the reason for the slow electron dynamics. KW - AG KW - Flims Y1 - 2020 U6 - https://doi.org/10.1103/PhysRevResearch.2.013343 SN - 0031-9007 VL - 2 IS - 1 SP - 1 EP - 9 PB - American Physical Society CY - Ridge, NY ER - TY - JOUR A1 - Gengel, Erik A1 - Pikovskij, Arkadij T1 - Phase reconstruction from oscillatory data with iterated Hilbert transform embeddings BT - benefits and limitations JF - Physica : D, Nonlinear phenomena N2 - In the data analysis of oscillatory systems, methods based on phase reconstruction are widely used to characterize phase-locking properties and inferring the phase dynamics. The main component in these studies is an extraction of the phase from a time series of an oscillating scalar observable. We discuss a practical procedure of phase reconstruction by virtue of a recently proposed method termed iterated Hilbert transform embeddings. We exemplify the potential benefits and limitations of the approach by applying it to a generic observable of a forced Stuart-Landau oscillator. Although in many cases, unavoidable amplitude modulation of the observed signal does not allow for perfect phase reconstruction, in cases of strong stability of oscillations and a high frequency of the forcing, iterated Hilbert transform embeddings significantly improve the quality of the reconstructed phase. We also demonstrate that for significant amplitude modulation, iterated embeddings do not provide any improvement. KW - Data analysis KW - Phase reconstruction KW - Hilbert transform Y1 - 2021 U6 - https://doi.org/10.1016/j.physd.2021.133070 SN - 0167-2789 SN - 1872-8022 VL - 429 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Stechemesser, Annika T1 - Human behaviour in a warming world BT - empirical evidence from social media and mobility data Y1 - 2023 ER - TY - JOUR A1 - Agarwal, Ankit A1 - Guntu, Ravikumar A1 - Banerjee, Abhirup A1 - Gadhawe, Mayuri Ashokrao A1 - Marwan, Norbert T1 - A complex network approach to study the extreme precipitation patterns in a river basin JF - Chaos : an interdisciplinary journal of nonlinear science N2 - The quantification of spatial propagation of extreme precipitation events is vital in water resources planning and disaster mitigation. However, quantifying these extreme events has always been challenging as many traditional methods are insufficient to capture the nonlinear interrelationships between extreme event time series. Therefore, it is crucial to develop suitable methods for analyzing the dynamics of extreme events over a river basin with a diverse climate and complicated topography. Over the last decade, complex network analysis emerged as a powerful tool to study the intricate spatiotemporal relationship between many variables in a compact way. In this study, we employ two nonlinear concepts of event synchronization and edit distance to investigate the extreme precipitation pattern in the Ganga river basin. We use the network degree to understand the spatial synchronization pattern of extreme rainfall and identify essential sites in the river basin with respect to potential prediction skills. The study also attempts to quantify the influence of precipitation seasonality and topography on extreme events. The findings of the study reveal that (1) the network degree is decreased in the southwest to northwest direction, (2) the timing of 50th percentile precipitation within a year influences the spatial distribution of degree, (3) the timing is inversely related to elevation, and (4) the lower elevation greatly influences connectivity of the sites. The study highlights that edit distance could be a promising alternative to analyze event-like data by incorporating event time and amplitude and constructing complex networks of climate extremes. Y1 - 2022 U6 - https://doi.org/10.1063/5.0072520 SN - 1054-1500 SN - 1089-7682 VL - 32 IS - 1 PB - American Institute of Physics CY - Woodbury, NY ER - TY - JOUR A1 - Mayer, Dennis A1 - Picconi, David A1 - Robinson, Matthew S. A1 - Gühr, Markus T1 - Experimental and theoretical gas-phase absorption spectra of thionated uracils JF - Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature N2 - We present a comparative study of the gas-phase UV spectra of uracil and its thionated counterparts (2-thiouracil, 4-thiouracil and 2,4-dithiouracil), closely supported by time-dependent density functional theory calculations to assign the transitions observed. We systematically discuss pure gas-phase spectra for the (thio)uracils in the range of 200-400 nm (similar to 3.2-6.4 eV), and examine the spectra of all four species with a single theoretical approach. We note that specific vibrational modelling is needed to accurately determine the spectra across the examined wavelength range, and systematically model the transitions that appear at wavelengths shorter than 250 nm. Additionally, we find in the cases of 2-thiouracil and 2,4-dithiouracil, that the gas-phase spectra deviate significantly from some previously published solution-phase spectra, especially those collected in basic environments. KW - Thiouracil KW - Uracil KW - UV-VIS Spectroscopy KW - Excited-state calculations; KW - TD-DFT KW - Gas phase Y1 - 2022 U6 - https://doi.org/10.1016/j.chemphys.2022.111500 SN - 0301-0104 VL - 558 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Fernández Serrano, Ricardo A1 - Saliwan-Neumann, Romeo A1 - Gonzalez-Doncel, Gaspar A1 - Bruno, Giovanni T1 - Dislocation substructures in pure aluminium after creep deformation as studied by electron backscatter diffraction JF - Journal of applied crystallography / International Union of Crystallography N2 - In the present work, electron backscatter diffraction was used to determine the microscopic dislocation structures generated during creep (with tests interrupted at the steady state) in pure 99.8% aluminium. This material was investigated at two different stress levels, corresponding to the power-law and power-law breakdown regimes. The results show that the formation of subgrain cellular structures occurs independently of the crystallographic orientation. However, the density of these cellular structures strongly depends on the grain crystallographic orientation with respect to the tensile axis direction, with (111) grains exhibiting the highest densities at both stress levels. It is proposed that this behaviour is due to the influence of intergranular stresses, which is different in (111) and (001) grains. KW - creep KW - pure aluminium KW - electron backscatter diffraction (EBSD) KW - cellular KW - structures KW - power law and power-law breakdown Y1 - 2022 U6 - https://doi.org/10.1107/S1600576722005209 SN - 1600-5767 VL - 55 SP - 860 EP - 869 PB - Munksgaard CY - Copenhagen ER - TY - GEN A1 - Poch, Olivier A1 - Istiqomah, Istiqomah A1 - Quirico, Eric A1 - Beck, Pierre A1 - Schmitt, Bernard A1 - Theulé, Patrice A1 - Faure, Alexandre A1 - Hily-Blant, Pierre A1 - Bonal, Lydie A1 - Kappel, David T1 - Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The measured nitrogen-to-carbon ratio in comets is lower than for the Sun, a discrepancy which could be alleviated if there is an unknown reservoir of nitrogen in comets. The nucleus of comet 67P/Churyumov-Gerasimenko exhibits an unidentified broad spectral reflectance feature around 3.2 micrometers, which is ubiquitous across its surface. On the basis of laboratory experiments, we attribute this absorption band to ammonium salts mixed with dust on the surface. The depth of the band indicates that semivolatile ammonium salts are a substantial reservoir of nitrogen in the comet, potentially dominating over refractory organic matter and more volatile species. Similar absorption features appear in the spectra of some asteroids, implying a compositional link between asteroids, comets, and the parent interstellar cloud. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1389 KW - resolution infrared-spectroscopy KW - ice absorption features KW - young stellar objects KW - exposed water ice KW - MU-M KW - bidirectional reflectance KW - murchison meteorite KW - interstellar ice KW - spectra KW - surface Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-513751 SN - 1866-8372 N1 - This secondary publication was withdrawn for copyright reasons. IS - 6483 ER - TY - JOUR A1 - Poch, Olivier A1 - Istiqomah, Istiqomah A1 - Quirico, Eric A1 - Beck, Pierre A1 - Schmitt, Bernard A1 - Theulé, Patrice A1 - Faure, Alexandre A1 - Hily-Blant, Pierre A1 - Bonal, Lydie A1 - Kappel, David T1 - Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids JF - Science N2 - The measured nitrogen-to-carbon ratio in comets is lower than for the Sun, a discrepancy which could be alleviated if there is an unknown reservoir of nitrogen in comets. The nucleus of comet 67P/Churyumov-Gerasimenko exhibits an unidentified broad spectral reflectance feature around 3.2 micrometers, which is ubiquitous across its surface. On the basis of laboratory experiments, we attribute this absorption band to ammonium salts mixed with dust on the surface. The depth of the band indicates that semivolatile ammonium salts are a substantial reservoir of nitrogen in the comet, potentially dominating over refractory organic matter and more volatile species. Similar absorption features appear in the spectra of some asteroids, implying a compositional link between asteroids, comets, and the parent interstellar cloud. KW - resolution infrared-spectroscopy KW - ice absorption features KW - young stellar objects KW - exposed water ice KW - MU-M KW - bidirectional reflectance KW - murchison meteorite KW - interstellar ice KW - spectra KW - surface Y1 - 2020 U6 - https://doi.org/10.1126/science.aaw7462 SN - 1095-9203 SN - 0036-8075 VL - 367 IS - 6483 SP - 1 EP - 8 PB - AAAS, American Association for the Advancement of Science CY - Washington, DC ER - TY - JOUR A1 - Gupta, Banshi D. A1 - Pathak, Anisha A1 - Shrivastav, Anand T1 - Optical Biomedical Diagnostics Using Lab-on-Fiber Technology BT - a review JF - Photonics : open access journal N2 - Point-of-care and in-vivo bio-diagnostic tools are the current need for the present critical scenarios in the healthcare industry. The past few decades have seen a surge in research activities related to solving the challenges associated with precise on-site bio-sensing. Cutting-edge fiber optic technology enables the interaction of light with functionalized fiber surfaces at remote locations to develop a novel, miniaturized and cost-effective lab on fiber technology for bio-sensing applications. The recent remarkable developments in the field of nanotechnology provide innumerable functionalization methodologies to develop selective bio-recognition elements for label free biosensors. These exceptional methods may be easily integrated with fiber surfaces to provide highly selective light-matter interaction depending on various transduction mechanisms. In the present review, an overview of optical fiber-based biosensors has been provided with focus on physical principles used, along with the functionalization protocols for the detection of various biological analytes to diagnose the disease. The design and performance of these biosensors in terms of operating range, selectivity, response time and limit of detection have been discussed. In the concluding remarks, the challenges associated with these biosensors and the improvement required to develop handheld devices to enable direct target detection have been highlighted. KW - fiber optic sensors KW - synthesis KW - interferometry KW - fluorescence KW - SERS KW - SPR KW - immunosensors KW - enzymatic sensors KW - molecular imprinted polymers Y1 - 2022 U6 - https://doi.org/10.3390/photonics9020086 SN - 2304-6732 VL - 9 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Kotz, Maximilian A1 - Levermann, Anders A1 - Wenz, Leonie T1 - The effect of rainfall changes on economic production JF - Nature : the international journal of science N2 - Macro-economic assessments of climate impacts lack an analysis of the distribution of daily rainfall, which can resolve both complex societal impact channels and anthropogenically forced changes(1-6). Here, using a global panel of subnational economic output for 1,554 regions worldwide over the past 40 years, we show that economic growth rates are reduced by increases in the number of wet days and in extreme daily rainfall, in addition to responding nonlinearly to the total annual and to the standardized monthly deviations of rainfall. Furthermore, high-income nations and the services and manufacturing sectors are most strongly hindered by both measures of daily rainfall, complementing previous work that emphasized the beneficial effects of additional total annual rainfall in low-income, agriculturally dependent economies(4,7). By assessing the distribution of rainfall at multiple timescales and the effects on different sectors, we uncover channels through which climatic conditions can affect the economy. These results suggest that anthropogenic intensification of daily rainfall extremes(8-10) will have negative global economic consequences that require further assessment by those who wish to evaluate the costs of anthropogenic climate change. Y1 - 2022 U6 - https://doi.org/10.1038/s41586-021-04283-8 SN - 0028-0836 SN - 1476-4687 VL - 601 IS - 7892 SP - 223 EP - 227 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - JOUR A1 - Schué, Emmanuelle A1 - Kopyshev, Alexey A1 - Lutz, Jean-François A1 - Börner, Hans G. T1 - Molecular bottle brushes with positioned selenols BT - Extending the toolbox of oxidative single polymer chain folding with conformation analysis by atomic force microscopy JF - Journal of Polymer Science N2 - A synthesis route to controlled and dynamic single polymer chain folding is reported. Sequence-controlled macromolecules containing precisely located selenol moieties within a polymer chain are synthesized. Oxidation of selenol functionalities lead to diselenide bridges and induces controlled intramolecular crosslinking to generate single chain collapse. The cyclization process is successfully characterized by SEC as well as by H-1 NMR and 2D HSQC NMR spectroscopies. In order to gain insight on the molecular level to reveal the degree of structural control, the folded polymers are transformed into folded molecular brushes that are known to be visualizable as single molecule structures by AFM. The "grafting onto" approach is performed by using triazolinedione-diene reaction to graft the side chain polymers. A series of folded molecular brushes as well as the corresponding linear controls are synthesized. AFM visualization is proving the cyclization of the folded backbone by showing globular objects, where non-folded brushes show typical worm-like structures. (C) 2019 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc. KW - atomic force microscopy (AFM) KW - diselenide KW - grafted polymers KW - molecular bottle brushes KW - sequence-controlled polymers KW - single chain folding Y1 - 2020 U6 - https://doi.org/10.1002/pola.29496 SN - 2642-4169 VL - 58 IS - 1 SP - 154 EP - 162 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Kirchartz, Thomas A1 - Márquez, José A. A1 - Stolterfoht, Martin A1 - Unold, Thomas T1 - Photoluminescence-based characterization of halide perovskites for photovoltaics JF - Advanced Energy Materials N2 - Photoluminescence spectroscopy is a widely applied characterization technique for semiconductor materials in general and halide perovskite solar cell materials in particular. It can give direct information on the recombination kinetics and processes as well as the internal electrochemical potential of free charge carriers in single semiconductor layers, layer stacks with transport layers, and complete solar cells. The correct evaluation and interpretation of photoluminescence requires the consideration of proper excitation conditions, calibration and application of the appropriate approximations to the rather complex theory, which includes radiative recombination, non-radiative recombination, interface recombination, charge transfer, and photon recycling. In this article, an overview is given of the theory and application to specific halide perovskite compositions, illustrating the variables that should be considered when applying photoluminescence analysis in these materials. KW - metal halide perovskites KW - numerical simulations KW - photoluminescence KW - photon recycling Y1 - 2020 U6 - https://doi.org/10.1002/aenm.201904134 SN - 1614-6832 SN - 1614-6840 VL - 10 IS - 26 SP - 1 EP - 21 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Steigert, Alexander A1 - Kojda, Sandrino Danny A1 - Ibaceta-Jaña, Josefa Fernanda A1 - Abou-Ras, Daniel A1 - Gunder, René A1 - Alktash, Nivin A1 - Habicht, Klaus A1 - Wagner, Markus Raphael A1 - Klenk, Reiner A1 - Raoux, Simone A1 - Szyszka, Bernd A1 - Lauermann, Iver A1 - Muydinov, Ruslan T1 - Water-assisted crystallization of amorphous indium zinc oxide films JF - Materials today. Communications N2 - Transparent conductive materials based on indium oxide remain yet irreplaceable in various optoelectronic applications. Amorphous oxides appear especially attractive for technology as they are isotropic, demonstrate relatively high electron mobility and can be processed at low temperatures. Among them is indium zinc oxide (IZO) with a large zinc content that is crucial for keeping the amorphous state but redundant for the doping. In this work we investigated water-free and water containing IZO films obtained by radio frequency sputtering. The correlation between temperature driven changes of the chemical state, the optical and electrical properties as well as the progression of crystallization was in focus. Such characterization methods as: scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, temperature dependent Hall-effect measurements and others were applied. Temperature dependent electrical properties of amorphous IZO and IZO:H2O films were found to evolve similarly. Based on our experience in In2O3:H2O (In2O3:H or IOH) we proposed an explanation for the changes observed. Water admixture was found to decrease crystallization temperature of IZO significantly from similar to 550 degrees C to similar to 280 degrees C. Herewith, the presence and concentration of water and/or hydroxyls was found to determine Zn distribution in the film. In particular, Zn enrichment was detected at the film's surface respective to the high water and/or hydroxyl amount. Raman spectra revealed a two-dimensional crystallization of w-ZnO which precedes regardless water presence an extensive In2O3 crystallization. An abrupt loss of electron mobility as a result of crystallization was attributed to the formation of ZnO interlayer on grain boundaries. KW - IZO KW - Thin films KW - TCOs KW - Crystallization KW - Water-assisted crystallization Y1 - 2022 U6 - https://doi.org/10.1016/j.mtcomm.2022.103213 SN - 2352-4928 VL - 31 PB - Elsevier CY - Amsterdam 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 - García-Benito, Inés A1 - Quarti, Claudio A1 - Queloz, Valentin I. E. A1 - Hofstetter, Yvonne J. A1 - Becker-Koch, David A1 - Caprioglio, Pietro A1 - Neher, Dieter A1 - Orlandi, Simonetta A1 - Cavazzini, Marco A1 - Pozzi, Gianluca A1 - Even, Jacky A1 - Nazeeruddin, Mohammad Khaja A1 - Vaynzof, Yana A1 - Grancini, Giulia T1 - Fluorination of organic spacer impacts on the structural and optical response of 2D perovskites JF - Frontiers in Chemistry N2 - Low-dimensional hybrid perovskites have triggered significant research interest due to their intrinsically tunable optoelectronic properties and technologically relevant material stability. In particular, the role of the organic spacer on the inherent structural and optical features in two-dimensional (2D) perovskites is paramount for material optimization. To obtain a deeper understanding of the relationship between spacers and the corresponding 2D perovskite film properties, we explore the influence of the partial substitution of hydrogen atoms by fluorine in an alkylammonium organic cation, resulting in (Lc)(2)PbI4 and (Lf)(2)PbI4 2D perovskites, respectively. Consequently, optical analysis reveals a clear 0.2 eV blue-shift in the excitonic position at room temperature. This result can be mainly attributed to a band gap opening, with negligible effects on the exciton binding energy. According to Density Functional Theory (DFT) calculations, the band gap increases due to a larger distortion of the structure that decreases the atomic overlap of the wavefunctions and correspondingly bandwidth of the valence and conduction bands. In addition, fluorination impacts the structural rigidity of the 2D perovskite, resulting in a stable structure at room temperature and the absence of phase transitions at a low temperature, in contrast to the widely reported polymorphism in some non-fluorinated materials that exhibit such a phase transition. This indicates that a small perturbation in the material structure can strongly influence the overall structural stability and related phase transition of 2D perovskites, making them more robust to any phase change. This work provides key information on how the fluorine content in organic spacer influence the structural distortion of 2D perovskites and their optical properties which possess remarkable importance for future optoelectronic applications, for instance in the field of light-emitting devices or sensors. KW - fluorinated organic spacer KW - 2D perovskites KW - phase transition KW - temperature dependence KW - excitonic materials Y1 - 2020 U6 - https://doi.org/10.3389/fchem.2019.00946 SN - 2296-2646 VL - 7 SP - 1 EP - 11 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Zhong, Yufei A1 - Causa, Martina A1 - Moore, Gareth John A1 - Krauspe, Philipp A1 - Xiao, Bo A1 - Günther, Florian A1 - Kublitski, Jonas A1 - BarOr, Eyal A1 - Zhou, Erjun A1 - Banerji, Natalie T1 - Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers JF - Nature Communications N2 - Organic photovoltaics based on non-fullerene acceptors (NFAs) show record efficiency of 16 to 17% and increased photovoltage owing to the low driving force for interfacial charge-transfer. However, the low driving force potentially slows down charge generation, leading to a tradeoff between voltage and current. Here, we disentangle the intrinsic charge-transfer rates from morphology-dependent exciton diffusion for a series of polymer:NFA systems. Moreover, we establish the influence of the interfacial energetics on the electron and hole transfer rates separately. We demonstrate that charge-transfer timescales remain at a few hundred femtoseconds even at near-zero driving force, which is consistent with the rates predicted by Marcus theory in the normal region, at moderate electronic coupling and at low re-organization energy. Thus, in the design of highly efficient devices, the energy offset at the donor:acceptor interface can be minimized without jeopardizing the charge-transfer rate and without concerns about a current-voltage tradeoff. KW - organic solar cell KW - electron-transfer KW - Donor-Acceptor (DA) interface KW - transfer dynamics KW - donor KW - seperation KW - efficiency KW - impact KW - energy KW - photovoltaics Y1 - 2020 U6 - https://doi.org/10.1038/s41467-020-14549-w SN - 2041-1723 VL - 11 IS - 1 SP - 1 EP - 10 PB - Nature Publishing Group UK CY - London ER - TY - JOUR A1 - Raman Venkatesan, Thulasinath A1 - Smykalla, David A1 - Ploss, Bernd A1 - Wübbenhorst, Michael A1 - Gerhard, Reimund T1 - Non-linear dielectric spectroscopy for detecting and evaluating structure-property relations in a P(VDF-TrFE-CFE) relaxor-ferroelectric terpolymer JF - Applied physics : A, Materials science & processing N2 - Non-linear dielectric spectroscopy (NLDS) is employed as an effective tool to study relaxation processes and phase transitions of a poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) relaxor-ferroelectric (R-F) terpolymer in detail. Measurements of the non-linear dielectric permittivity epsilon 2 ' reveal peaks at 30 and 80 degrees C that cannot be identified in conventional dielectric spectroscopy. By combining the results from NLDS experiments with those from other techniques such as thermally stimulated depolarization and dielectric-hysteresis studies, it is possible to explain the processes behind the additional peaks. The former peak, which is associated with the mid-temperature transition, is found in all other vinylidene fluoride-based polymers and may help to understand the non-zero epsilon 2 ' values that are detected on the paraelectric phase of the terpolymer. The latter peak can also be observed during cooling of P(VDF-TrFE) copolymer samples at 100 degrees C and is due to conduction and space-charge polarization as a result of the accumulation of real charges at the electrode-sample interface. KW - Non-linear dielectric spectroscopy KW - P(VDF-TrFE-CFE) KW - Relaxor-ferroelectric polymer KW - Dielectric hysteresis KW - Curie-transition KW - Mid-temperature transition Y1 - 2021 U6 - https://doi.org/10.1007/s00339-021-04876-0 SN - 0947-8396 SN - 1432-0630 VL - 127 IS - 10 PB - Springer CY - Berlin ; Heidelberg ; New York ER - TY - JOUR A1 - Tokmoldin, Nurlan A1 - Vollbrecht, Joachim A1 - Hosseini, Seyed Mehrdad A1 - Sun, Bowen A1 - Perdigón-Toro, Lorena A1 - Woo, Han Young A1 - Zou, Yingping A1 - Neher, Dieter A1 - Shoaee, Safa T1 - Explaining the fill-factor and photocurrent losses of nonfullerene acceptor-based solar cells by probing the long-range charge carrier diffusion and drift lengths JF - Advanced energy materials N2 - Organic solar cells (OSC) nowadays match their inorganic competitors in terms of current production but lag behind with regards to their open-circuit voltage loss and fill-factor, with state-of-the-art OSCs rarely displaying fill-factor of 80% and above. The fill-factor of transport-limited solar cells, including organic photovoltaic devices, is affected by material and device-specific parameters, whose combination is represented in terms of the established figures of merit, such as theta and alpha. Herein, it is demonstrated that these figures of merit are closely related to the long-range carrier drift and diffusion lengths. Further, a simple approach is presented to devise these characteristic lengths using steady-state photoconductance measurements. This yields a straightforward way of determining theta and alpha in complete cells and under operating conditions. This approach is applied to a variety of photovoltaic devices-including the high efficiency nonfullerene acceptor blends-and show that the diffusion length of the free carriers provides a good correlation with the fill-factor. It is, finally, concluded that most state-of-the-art organic solar cells exhibit a sufficiently large drift length to guarantee efficient charge extraction at short circuit, but that they still suffer from too small diffusion lengths of photogenerated carriers limiting their fill factor. KW - diffusion length KW - drift length KW - figure of merit KW - lifetime‐ mobility product KW - steady‐ state photoconductance Y1 - 2021 U6 - https://doi.org/10.1002/aenm.202100804 SN - 1614-6840 VL - 11 IS - 22 PB - Wiley-VCH CY - Weinheim ER -