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 - TY - JOUR A1 - Schlemm, Tanja A1 - Levermann, Anders T1 - A simple parametrization of mélange buttressing for calving glaciers JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Both ice sheets in Greenland and Antarctica are discharging ice into the ocean. In many regions along the coast of the ice sheets, the icebergs calve into a bay. If the addition of icebergs through calving is faster than their transport out of the embayment, the icebergs will be frozen into a melange with surrounding sea ice in winter. In this case, the buttressing effect of the ice melange can be considerably stronger than any buttressing by mere sea ice would be. This in turn stabilizes the glacier terminus and leads to a reduction in calving rates. Here we propose a simple parametrization of ice melange buttressing which leads to an upper bound on calving rates and can be used in numerical and analytical modelling. Y1 - 2021 U6 - https://doi.org/10.5194/tc-15-531-2021 SN - 1994-0416 SN - 1994-0424 VL - 15 IS - 2 SP - 531 EP - 545 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Grischek, Max A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Gutierrez-Partida, Emilio A1 - Peña-Camargo, Francisco A1 - Rothhardt, Daniel A1 - Zhang, Shanshan A1 - Raoufi, Meysam A1 - Wolansky, Jakob A1 - Abdi-Jalebi, Mojtaba A1 - Stranks, Samuel D. A1 - Albrecht, Steve A1 - Kirchartz, Thomas A1 - Neher, Dieter T1 - How to quantify the efficiency potential of neat perovskite films BT - Perovskite semiconductors with an implied efficiency exceeding 28% JF - Advanced Materials N2 - Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit. KW - non-radiative interface recombination KW - perovskite solar cells KW - photoluminescence Y1 - 2020 U6 - https://doi.org/10.1002/adma.202000080 SN - 0935-9648 SN - 1521-4095 VL - 32 IS - 17 SP - 1 EP - 10 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mohammady, M. Hamed A1 - Auffèves, Alexia A1 - Anders, Janet T1 - Energetic footprints of irreversibility in the quantum regime JF - Communications Physics N2 - In classical thermodynamic processes the unavoidable presence of irreversibility, quantified by the entropy production, carries two energetic footprints: the reduction of extractable work from the optimal, reversible case, and the generation of a surplus of heat that is irreversibly dissipated to the environment. Recently it has been shown that in the quantum regime an additional quantum irreversibility occurs that is linked to decoherence into the energy basis. Here we employ quantum trajectories to construct distributions for classical heat and quantum heat exchanges, and show that the heat footprint of quantum irreversibility differs markedly from the classical case. We also quantify how quantum irreversibility reduces the amount of work that can be extracted from a state with coherences. Our results show that decoherence leads to both entropic and energetic footprints which both play an important role in the optimization of controlled quantum operations at low temperature. In classical thermodynamics irreversibility occurs whenever a non-thermal system is brought into contact with a thermal environment. Using quantum trajectories the authors here establish two energetic footprints of quantum irreversible processes, and find that while quantum irreversibility leads to the occurrence of a quantum heat and a reduction of work production, the two are not linked in the same manner as the classical laws of thermodynamics would dictate. KW - entropy production KW - quantum mechanics KW - thermodynamics Y1 - 2020 U6 - https://doi.org/10.1038/s42005-020-0356-9 SN - 2399-3650 VL - 3 IS - 1 SP - 1 EP - 14 PB - Springer Nature CY - London ER - TY - JOUR A1 - Horton, Benjamin P. A1 - Khan, Nicole S. A1 - Cahill, Niamh A1 - Lee, Janice S. H. A1 - Shaw, Timothy A. A1 - Garner, Andra J. A1 - Kemp, Andrew C. A1 - Engelhart, Simon E. A1 - Rahmstorf, Stefan T1 - Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from an expert survey JF - npj Climate and Atmospheric Science N2 - Sea-level rise projections and knowledge of their uncertainties are vital to make informed mitigation and adaptation decisions. To elicit projections from members of the scientific community regarding future global mean sea-level (GMSL) rise, we repeated a survey originally conducted five years ago. Under Representative Concentration Pathway (RCP) 2.6, 106 experts projected a likely (central 66% probability) GMSL rise of 0.30-0.65 m by 2100, and 0.54-2.15 m by 2300, relative to 1986-2005. Under RCP 8.5, the same experts projected a likely GMSL rise of 0.63-1.32 m by 2100, and 1.67-5.61 m by 2300. Expert projections for 2100 are similar to those from the original survey, although the projection for 2300 has extended tails and is higher than the original survey. Experts give a likelihood of 42% (original survey) and 45% (current survey) that under the high-emissions scenario GMSL rise will exceed the upper bound (0.98 m) of the likely range estimated by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, which is considered to have an exceedance likelihood of 17%. Responses to open-ended questions suggest that the increases in upper-end estimates and uncertainties arose from recent influential studies about the impact of marine ice cliff instability on the meltwater contribution to GMSL rise from the Antarctic Ice Sheet. KW - projections KW - Greenland KW - consequences KW - climate Y1 - 2020 U6 - https://doi.org/10.1038/s41612-020-0121-5 SN - 2397-3722 VL - 3 IS - 1 SP - 1 EP - 8 PB - Springer Nature CY - London ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Safdari, Hadiseh A1 - Metzler, Ralf T1 - Anomalous diffusion, nonergodicity, and ageing for exponentially and logarithmically time-dependent diffusivity BT - striking differences for massive versus massless particles JF - Journal of physics. D, Applied physics N2 - We investigate a diffusion process with a time-dependent diffusion coefficient, both exponentially increasing and decreasing in time, D(t)=D-0(e +/- 2 alpha t). For this (hypothetical) nonstationary diffusion process we compute-both analytically and from extensive stochastic simulations-the behavior of the ensemble- and time-averaged mean-squared displacements (MSDs) of the particles, both in the over- and underdamped limits. Simple asymptotic relations derived for the short- and long-time behaviors are shown to be in excellent agreement with the results of simulations. The diffusive characteristics in the presence of ageing are also considered, with dramatic differences of the over- versus underdamped regime. Our results for D(t)=D-0(e +/- 2 alpha t) extend and generalize the class of diffusive systems obeying scaled Brownian motion featuring a power-law-like variation of the diffusivity with time, D(t) similar to t(alpha-1). We also examine the logarithmically increasing diffusivity, D(t)=D(0)log[t/tau(0)], as another fundamental functional dependence (in addition to the power-law and exponential) and as an example of diffusivity slowly varying in time. One of the main conclusions is that the behavior of the massive particles is predominantly ergodic, while weak ergodicity breaking is repeatedly found for the time-dependent diffusion of the massless particles at short times. The latter manifests itself in the nonequivalence of the (both nonaged and aged) MSD and the mean time-averaged MSD. The current findings are potentially applicable to a class of physical systems out of thermal equilibrium where a rapid increase or decrease of the particles' diffusivity is inherently realized. One biological system potentially featuring all three types of time-dependent diffusion (power-law-like, exponential, and logarithmic) is water diffusion in the brain tissues, as we thoroughly discuss in the end. KW - anomalous diffusion KW - scaled Brownian motion KW - stochastic processes KW - nonstationary diffusivity KW - water diffusion in the brain KW - nonergodicity Y1 - 2021 U6 - https://doi.org/10.1088/1361-6463/abdff0 SN - 0022-3727 SN - 1361-6463 VL - 54 IS - 19 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Gieg, Henrique A1 - Schianchi, Federico A1 - Dietrich, Tim A1 - Ujevic, Maximiliano T1 - Incorporating a Radiative Hydrodynamics Scheme in the Numerical-Relativity Code BAM JF - Universe : open access journal N2 - To study binary neutron star systems and to interpret observational data such as gravitational-wave and kilonova signals, one needs an accurate description of the processes that take place during the final stages of the coalescence, for example, through numerical-relativity simulations. In this work, we present an updated version of the numerical-relativity code BAM in order to incorporate nuclear-theory-based equations of state and a simple description of neutrino interactions through a neutrino leakage scheme. Different test simulations, for stars undergoing a neutrino-induced gravitational collapse and for binary neutron stars systems, validate our new implementation. For the binary neutron stars systems, we show that we can evolve stably and accurately distinct microphysical models employing the different equations of state: SFHo, DD2, and the hyperonic BHB Lambda phi. Overall, our test simulations have good agreement with those reported in the literature. KW - numerical relativity KW - binary neutron stars KW - neutrinos KW - leakage scheme Y1 - 2022 U6 - https://doi.org/10.3390/universe8070370 SN - 2218-1997 VL - 8 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Letellier, Christophe A1 - Abraham, Ralph A1 - Shepelyansky, Dima L. A1 - Rossler, Otto E. A1 - Holmes, Philip A1 - Lozi, Rene A1 - Glass, Leon A1 - Pikovsky, Arkady A1 - Olsen, Lars F. A1 - Tsuda, Ichiro A1 - Grebogi, Celso A1 - Parlitz, Ulrich A1 - Gilmore, Robert A1 - Pecora, Louis M. A1 - Carroll, Thomas L. T1 - Some elements for a history of the dynamical systems theory JF - Chaos : an interdisciplinary journal of nonlinear science N2 - Writing a history of a scientific theory is always difficult because it requires to focus on some key contributors and to "reconstruct" some supposed influences. In the 1970s, a new way of performing science under the name "chaos" emerged, combining the mathematics from the nonlinear dynamical systems theory and numerical simulations. To provide a direct testimony of how contributors can be influenced by other scientists or works, we here collected some writings about the early times of a few contributors to chaos theory. The purpose is to exhibit the diversity in the paths and to bring some elements-which were never published-illustrating the atmosphere of this period. Some peculiarities of chaos theory are also discussed. Y1 - 2021 U6 - https://doi.org/10.1063/5.0047851 SN - 1054-1500 SN - 1089-7682 VL - 31 IS - 5 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Mani, Deepak A1 - Kupsch, Andreas A1 - Müller, Bernd R. A1 - Bruno, Giovanni T1 - Diffraction Enhanced Imaging Analysis with Pseudo-Voigt Fit Function JF - Journal of imaging : open access journal N2 - Diffraction enhanced imaging (DEI) is an advanced digital radiographic imaging technique employing the refraction of X-rays to contrast internal interfaces. This study aims to qualitatively and quantitatively evaluate images acquired using this technique and to assess how different fitting functions to the typical rocking curves (RCs) influence the quality of the images. RCs are obtained for every image pixel. This allows the separate determination of the absorption and the refraction properties of the material in a position-sensitive manner. Comparison of various types of fitting functions reveals that the Pseudo-Voigt (PsdV) function is best suited to fit typical RCs. A robust algorithm was developed in the Python programming language, which reliably extracts the physically meaningful information from each pixel of the image. We demonstrate the potential of the algorithm with two specimens: a silicone gel specimen that has well-defined interfaces, and an additively manufactured polycarbonate specimen. KW - diffraction enhanced imaging KW - analyzer-based imaging KW - X-ray refraction; KW - non-destructive evaluation KW - Pseudo-Voigt fit function KW - Python Y1 - 2022 U6 - https://doi.org/10.3390/jimaging8080206 SN - 2313-433X VL - 8 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Meyer, Dominique M.-A. A1 - Velazquez, Pablo F. A1 - Petruk, Oleh A1 - Chiotellis, Alexandros A1 - Pohl, Martin A1 - Camps-Farina, Artemi A1 - Petrov, Miroslav A1 - Reynoso, Estela M. A1 - Toledo-Roy, Juan C. A1 - Schneiter, E. Matias A1 - Castellanos-Ramirez, Antonio A1 - Esquivel, Alejandro T1 - Rectangular core-collapse supernova remnants BT - application to Puppis A JF - Monthly notices of the Royal Astronomical Society N2 - Core-collapse supernova remnants are the gaseous nebulae of galactic interstellar media (ISM) formed after the explosive death of massive stars. Their morphology and emission properties depend both on the surrounding circumstellar structure shaped by the stellar wind-ISM interaction of the progenitor star and on the local conditions of the ambient medium. In the warm phase of the Galactic plane (n approximate to 1 cm(-3), T approximate to 8000 K), an organized magnetic field of strength 7 mu G has profound consequences on the morphology of the wind bubble of massive stars at rest. In this paper, we show through 2.5D magnetohydrodynamical simulations, in the context of a Wolf-Rayet-evolving 35 M 0 star, that it affects the development of its supernova remnant. When the supernova remnant reaches its middle age (15-20 kyr), it adopts a tubular shape that results from the interaction between the isotropic supernova ejecta and the anisotropic, magnetized, shocked stellar progenitor bubble into which the supernova blast wave expands. Our calculations for non-thermal emission, i.e. radio synchrotron and inverse-Compton radiation, reveal that such supernova remnants can, due to projection effects, appear as rectangular objects in certain cases. This mechanism for shaping a supernova remnant is similar to the bipolar and elliptical planetary nebula production by wind-wind interaction in the low-mass regime of stellar evolution. If such a rectangular core-collapse supernova remnant is created, the progenitor star must not have been a runaway star. We propose that such a mechanism is at work in the shaping of the asymmetric core-collapse supernova remnant Puppis A. KW - stars: evolution KW - stars: massive KW - ISM: supernova remnants KW - methods: MHD Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac1832 SN - 0035-8711 SN - 1365-2966 VL - 515 IS - 1 SP - 594 EP - 605 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Nedora, Vsevolod A1 - Radice, David A1 - Bernuzzi, Sebastiano A1 - Perego, Albino A1 - Daszuta, Boris A1 - Endrizzi, Andrea A1 - Prakash, Aviral A1 - Schianchi, Federico T1 - Dynamical ejecta synchrotron emission as a possible contributor to the changing behaviour of GRB170817A afterglow JF - Monthly notices of the Royal Astronomical Society N2 - Over the past 3 yr, the fading non-thermal emission from the GW170817 remained generally consistent with the afterglow powered by synchrotron radiation produced by the interaction of the structured jet with the ambient medium. Recent observations by Hajela et al. indicate the change in temporal and spectral behaviour in the X-ray band. We show that the new observations are compatible with the emergence of a new component due to non-thermal emission from the fast tail of the dynamical ejecta of ab-initio binary neutron star merger simulations. This provides a new avenue to constrain binary parameters. Specifically, we find that equal mass models with soft equations of state (EOSs) and high-mass ratio models with stiff EOSs are disfavoured as they typically predict afterglows that peak too early to explain the recent observations. Moderate stiffness and mass ratio models, instead, tend to be in good overall agreement with the data. KW - equation of state KW - gravitational waves KW - neutron star mergers Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab2004 SN - 0035-8711 SN - 1365-2966 VL - 506 IS - 4 SP - 5908 EP - 5915 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Hornemann, Andrea A1 - Eichert, Diane Madeleine A1 - Hoehl, Arne A1 - Tiersch, Brigitte A1 - Ulm, Gerhard A1 - Ryadnov, Maxim G. A1 - Beckhoff, Burkhard T1 - Investigating Membrane-Mediated Antimicrobial Peptide Interactions with Synchrotron Radiation Far-Infrared Spectroscopy JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - Synchrotron radiation-based Fourier transform infrared spectroscopy enables access to vibrational information from mid over far infrared to even terahertz domains. This information may prove critical for the elucidation of fundamental bio-molecular phenomena including folding-mediated innate host defence mechanisms. Antimicrobial peptides (AMPs) represent one of such phenomena. These are major effector molecules of the innate immune system, which favour attack on microbial membranes. AMPs recognise and bind to the membranes whereupon they assemble into pores or channels destabilising the membranes leading to cell death. However, specific molecular interactions responsible for antimicrobial activities have yet to be fully understood. Herein we probe such interactions by assessing molecular specific variations in the near-THz 400-40 cm(-1) range for defined helical AMP templates in reconstituted phospholipid membranes. In particular, we show that a temperature-dependent spectroscopic analysis, supported by 2D correlative tools, provides direct evidence for the membrane-induced and folding-mediated activity of AMPs. The far-FTIR study offers a direct and information-rich probe of membrane-related antimicrobial interactions. KW - antimicrobial peptides KW - electrostatic interactions KW - IR spectroscopy KW - phospholipid membranes KW - protein folding Y1 - 2022 U6 - https://doi.org/10.1002/cphc.202100815 SN - 1439-4235 SN - 1439-7641 VL - 23 IS - 4 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Toalá, Jesús Alberto A1 - Bowman, Dominic A1 - Van Reeth, Timothy A1 - Todt, Helge Tobias A1 - Dsilva, Karan A1 - Shenar, Tomer A1 - Koenigsberger, Gloria Suzanne A1 - Estrada-Dorado, Sandino A1 - Oskinova, Lida A1 - Hamann, Wolf-Rainer T1 - Multiple variability time-scales of the early nitrogen-rich Wolf-Rayet star WR 7 JF - Monthly notices of the Royal Astronomical Society N2 - We present the analysis of the optical variability of the early, nitrogen-rich Wolf-Rayet (WR) star WR 7. The analysis of multisector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multiperiodic variability that is modulated on time-scales of years. We detect a dominant period of 2.6433 +/- 0.0005 d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR 7, including pulsations, binarity, co-rotating interaction regions (CIRs), and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR 7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR 7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short (less than or similar to 1 d) and long (greater than or similar to 1000 d) variability time-scales. KW - stars: atmospheres KW - stars: evolution KW - stars: individual: WR 7 KW - stars: winds KW - outflows KW - stars: Wolft-Rayet Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac1455 SN - 0035-8711 SN - 1365-2966 VL - 514 IS - 2 SP - 2269 EP - 2277 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Zaragoza-Cardiel, Javier A1 - Gómez-González, Víctor Mauricio Alfonso A1 - Mayya, Yalia Divakara A1 - Ramos-Larios, Gerardo T1 - Nebular abundance gradient in the Cartwheel galaxy using MUSE data JF - Monthly notices of the Royal Astronomical Society N2 - We here present the results from a detailed analysis of nebular abundances of commonly observed ions in the collisional ring galaxy Cartwheel using the Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) data set. The analysis includes 221 H II regions in the star-forming ring, in addition to 40 relatively fainter H a-emitting regions in the spokes, disc, and the inner ring. The ionic abundances of He, N, O, and Fe are obtained using the direct method (DM) for 9, 20, 20, and 17 ring H II regions, respectively, where the S++ temperature-sensitive line is detected. For the rest of the regions, including all the nebulae between the inner and the outer ring, we obtained O abundances using the strong-line method (SLM). The ring regions have a median 12 + log O/H = 8.19 +/- 0.15, log N/O = -1.57 +/- 0.09 and log Fe/O = -2.24 +/- 0.09 using the DM. Within the range of O abundances seen in the Cartwheel, the N/O and Fe/O values decrease proportionately with increasing O, suggesting local enrichment of O without corresponding enrichment of primary N and Fe. The O abundances of the disc H II regions obtained using the SLM show a well-defined radial gradient. The mean O abundance of the ring H II regions is lower by similar to 0.1 dex as compared to the extrapolation of the radial gradient. The observed trends suggest the preservation of the pre-collisional abundance gradient, displacement of most of the processed elements to the ring, as predicted by the recent simulation by Renaud et al., and post-collisional infall of metal-poor gas in the ring. KW - galaxies: star clusters KW - galaxies: individual KW - galaxies: abundances Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac1423 SN - 0035-8711 SN - 1365-2966 VL - 514 IS - 2 SP - 1689 EP - 1705 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Meyer, Philipp A1 - Aghion, Erez A1 - Kantz, Holger T1 - Decomposing the effect of anomalous diffusion enables direct calculation of the Hurst exponent and model classification for single random paths JF - Journal of physics / Institute of Physics. A, Mathematical, nuclear and general N2 - Recently, a large number of research teams from around the world collaborated in the so-called 'anomalous diffusion challenge'. Its aim: to develop and compare new techniques for inferring stochastic models from given unknown time series, and estimate the anomalous diffusion exponent in data. We use various numerical methods to directly obtain this exponent using the path increments, and develop a questionnaire for model selection based on feature analysis of a set of known stochastic processes given as candidates. Here, we present the theoretical background of the automated algorithm which we put for these tasks in the diffusion challenge, as a counter to other pure data-driven approaches. KW - time-series analysis KW - decomposing anomalous diffusion KW - anomalous KW - diffusion exponent KW - process inference Y1 - 2022 U6 - https://doi.org/10.1088/1751-8121/ac72d4 SN - 1751-8113 SN - 1751-8121 VL - 55 IS - 27 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Bolotov, Dmitry A1 - Bolotov, Maxim I. A1 - Smirnov, Lev A. A1 - Osipov, Grigory V. A1 - Pikovsky, Arkady T1 - Synchronization regimes in an ensemble of phase oscillators coupled through a diffusion field JF - Radiophysics and quantum electronics N2 - We consider an ensemble of identical phase oscillators coupled through a common diffusion field. Using the Ott-Antonsen reduction, we develop dynamical equations for the complex local order parameter and the mean field. The regions of the existence and stability are determined for the totally synchronous, partially synchronous, and asynchronous spatially homogeneous states. A procedure of searching for inhomogeneous states as periodic trajectories of an auxiliary system of the ordinary differential equations is demonstrated. A scenario of emergence of chimera structures from homogeneous synchronous solutions is described. Y1 - 2022 U6 - https://doi.org/10.1007/s11141-022-10173-4 SN - 0033-8443 SN - 1573-9120 VL - 64 IS - 10 SP - 709 EP - 725 PB - Springer CY - New York ER - TY - JOUR A1 - Schaffenroth, Veronika A1 - Casewell, Sarah L. A1 - Schneider, D. A1 - Kilkenny, David A1 - Geier, Stephan A1 - Heber, Ulrich A1 - Irrgang, Andreas A1 - Przybilla, Norbert A1 - Marsh, Thomas R. A1 - Littlefair, Stuart P. A1 - Dhillon, Vik S. T1 - A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era JF - Monthly notices of the Royal Astronomical Society N2 - Subdwarf B stars are core-helium-burning stars located on the extreme horizontal branch (EHB). Extensive mass loss on the red giant branch is necessary to form them. It has been proposed that substellar companions could lead to the required mass loss when they are engulfed in the envelope of the red giant star. J08205+0008 was the first example of a hot subdwarf star with a close, substellar companion candidate to be found. Here, we perform an in-depth re-analysis of this important system with much higher quality data allowing additional analysis methods. From the higher resolution spectra obtained with ESO-VLT/XSHOOTER, we derive the chemical abundances of the hot subdwarf as well as its rotational velocity. Using the Gaia parallax and a fit to the spectral energy distribution in the secondary eclipse, tight constraints to the radius of the hot subdwarf are derived. From a long-term photometric campaign, we detected a significant period decrease of -3.2(8) x 10(-12) dd(-1). This can be explained by the non-synchronized hot subdwarf star being spun up by tidal interactions forcing it to become synchronized. From the rate of period decrease we could derive the synchronization time-scale to be 4 Myr, much smaller than the lifetime on EHB. By combining all different methods, we could constrain the hot subdwarf to a mass of 0.39-0.50 M-circle dot and a radius of R-sdB = 0.194 +/- 0.008 R-circle dot, and the companion to 0.061-0.071 M-circle dot with a radius of R-comp = 0.092 +/- 0.005 R-circle dot, below the hydrogen-burning limit. We therefore confirm that the companion is most likely a massive brown dwarf. KW - stars: abundances KW - stars: atmospheres KW - stars: fundamental parameters KW - stars: horizontal branch KW - stars: low-mass KW - subdwarfs Y1 - 2020 U6 - https://doi.org/10.1093/mnras/staa3661 SN - 0035-8711 SN - 1365-2966 VL - 501 IS - 3 SP - 3847 EP - 3870 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Thomas, Timon A1 - Pfrommer, Christoph A1 - Pakmor, Rüdiger T1 - A finite volume method for two-moment cosmic ray hydrodynamics on a moving mesh JF - Monthly notices of the Royal Astronomical Society N2 - We present a new numerical algorithm to solve the recently derived equations of two-moment cosmic ray hydrodynamics (CRHD). The algorithm is implemented as a module in the moving mesh AREPO code. Therein, the anisotropic transport of cosmic rays (CRs) along magnetic field lines is discretized using a path-conservative finite volume method on the unstructured time-dependent Voronoi mesh of AREPO. The interaction of CRs and gyroresonant Alfven waves is described by short time-scale source terms in the CRHD equations. We employ a custom-made semi-implicit adaptive time stepping source term integrator to accurately integrate this interaction on the small light-crossing time of the anisotropic transport step. Both the transport and the source term integration step are separated from the evolution of the magnetohydrodynamical equations using an operator split approach. The new algorithm is tested with a variety of test problems, including shock tubes, a perpendicular magnetized discontinuity, the hydrodynamic response to a CR overpressure, CR acceleration of a warm cloud, and a CR blast wave, which demonstrate that the coupling between CR and magnetohydrodynamics is robust and accurate. We demonstrate the numerical convergence of the presented scheme using new linear and non-linear analytic solutions. KW - hydrodynamics KW - MHD KW - methods: numerical KW - cosmic rays Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab397 SN - 0035-8711 SN - 1365-2966 VL - 503 IS - 2 SP - 2242 EP - 2264 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Pikovskij, Arkadij T1 - Synchronization of oscillators with hyperbolic chaotic phases JF - Izvestija vysšich učebnych zavedenij : naučno-techničeskij žurnal = Izvestiya VUZ. Prikladnaja nelinejnaja dinamika = Applied nonlinear dynamics N2 - Topic and aim. Synchronization in populations of coupled oscillators can be characterized with order parameters that describe collective order in ensembles. A dependence of the order parameter on the coupling constants is well-known for coupled periodic oscillators. The goal of the study is to extend this analysis to ensembles of oscillators with chaotic phases, moreover with phases possessing hyperbolic chaos. Models and methods. Two models are studied in the paper. One is an abstract discrete-time map, composed with a hyperbolic Bernoulli transformation and with Kuramoto dynamics. Another model is a system of coupled continuous-time chaotic oscillators, where each individual oscillator has a hyperbolic attractor of Smale-Williams type. Results. The discrete-time model is studied with the Ott-Antonsen ansatz, which is shown to be invariant under the application of the Bernoulli map. The analysis of the resulting map for the order parameter shows, that the asynchronouis state is always stable, but the synchronous one becomes stable above a certain coupling strength. Numerical analysis of the continuous-time model reveals a complex sequence of transitions from an asynchronous state to a completely synchronous hyperbolic chaos, with intermediate stages that include regimes with periodic in time mean field, as well as with weakly and strongly irregular mean field variations. Discussion. Results demonstrate that synchronization of systems with hyperbolic chaos of phases is possible, although a rather strong coupling is required. The approach can be applied to other systems of interacting units with hyperbolic chaotic dynamics. N2 - Тема и цель. Синхронизация в популяциях связанных осцилляторов может быть охарактеризована параметрами порядка, описывающими коллективный порядок в ансамблях. Зависимость параметра порядка от коэффициентов связи хорошо известна для связанных периодических осцилляторов. Целью данного исследования является обобщение этого анализа на ансамбли осцилляторов с хаотическими фазами, а именно, с фазами, распределёнными на гиперболическом аттракторе. Модели и методы. В работе исследуются две модели. Первая – абстрактное отображение в дискретном времени, составленное из гиперболического преобразования Бернулли и динамики Курамото. Вторая – это система связанных хаотических осцилляторов в непрерывном времени, где каждый отдельный осциллятор имеет гиперболический аттрактор типа Смейла–Вильямса. Результаты. Модель в дискретном времени изучается с помощью подхода Отта–Антонсена, который, как показано, инвариантен при применении отображения Бернулли. Анализ полученного отображения по параметрам порядка показывает, что асинхронное состояние всегда устойчиво, а синхронное состояние становится устойчивым выше определенной силы связи. Численный анализ модели в непрерывном времени показывает сложную последовательность переходов из асинхронного состояния в полностью синхронный гиперболический хаос с промежуточными стадиями, которые включают режимы с периодическим во времени средним полем, а также со слабо и сильно нерегулярными вариациями среднего поля. Обсуждение. Результаты показывают, что синхронизация систем с гиперболическим фазовым хаосом возможна, хотя требуется довольно сильная связь. Данный подход может быть применен и к другим системам взаимодействующих звеньев с гиперболической хаотической динамикой. T2 - Синхронизация осцилляторов с гиперболическими хаотическими фазами KW - hyperbolic attractor KW - synchronization KW - collective dynamics KW - иперболический аттрактор KW - синхронизация KW - оллективная динамика Y1 - 2021 U6 - https://doi.org/10.18500/0869-6632-2021-29-1-78-87 SN - 0869-6632 SN - 2542-1905 VL - 29 IS - 1 SP - 78 EP - 87 PB - Saratov State University CY - Saratov ER - TY - JOUR A1 - Rosenau, Philip A1 - Pikovskij, Arkadij T1 - Waves in strongly nonlinear Gardner-like equations on a lattice JF - Nonlinearity / the Institute of Physics and the London Mathematical Society N2 - We introduce and study a family of lattice equations which may be viewed either as a strongly nonlinear discrete extension of the Gardner equation, or a non-convex variant of the Lotka-Volterra chain. Their deceptively simple form supports a very rich family of complex solitary patterns. Some of these patterns are also found in the quasi-continuum rendition, but the more intriguing ones, like interlaced pairs of solitary waves, or waves which may reverse their direction either spontaneously or due a collision, are an intrinsic feature of the discrete realm. KW - nonlinear lattice KW - solitary wave KW - Gardner equation KW - compacton Y1 - 2021 U6 - https://doi.org/10.1088/1361-6544/ac0f51 SN - 0951-7715 SN - 1361-6544 VL - 34 IS - 8 SP - 5872 EP - 5896 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Bekir, Marek A1 - Jelken, Joachim A1 - Jung, Se-Hyeong A1 - Pich, Andrij A1 - Pacholski, Claudia A1 - Kopyshev, Alexey A1 - Santer, Svetlana T1 - Dual responsiveness of microgels induced by single light stimulus JF - Applied physics letters N2 - We report on the multiple response of microgels triggered by a single optical stimulus. Under irradiation, the volume of the microgels is reversibly switched by more than 20 times. The irradiation initiates two different processes: photo-isomerization of the photo-sensitive surfactant, which forms a complex with the anionic microgel, rendering it photo-responsive; and local heating due to a thermo-plasmonic effect within the structured gold layer on which the microgel is deposited. The photo-responsivity is related to the reversible accommodation/release of the photo-sensitive surfactant depending on its photo-isomerization state, while the thermo-sensitivity is intrinsically built in. We show that under exposure to green light, the thermo-plasmonic effect generates a local hot spot in the gold layer, resulting in the shrinkage of the microgel. This process competes with the simultaneous photo-induced swelling. Depending on the position of the laser spot, the spatiotemporal control of reversible particle shrinking/swelling with a predefined extent on a per-second base can be implemented. Y1 - 2021 U6 - https://doi.org/10.1063/5.0036376 SN - 0003-6951 SN - 1077-3118 VL - 118 IS - 9 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Morris, Paul J. A1 - Bohdan, Artem A1 - Weidl, Martin S. A1 - Pohl, Martin T1 - Preacceleration in the Electron Foreshock. I. Electron Acoustic Waves JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - To undergo diffusive shock acceleration, electrons need to be preaccelerated to increase their energies by several orders of magnitude, else their gyroradii will be smaller than the finite width of the shock. In oblique shocks, where the upstream magnetic field orientation is neither parallel nor perpendicular to the shock normal, electrons can escape to the shock upstream, modifying the shock foot to a region called the electron foreshock. To determine the preacceleration in this region, we undertake particle-in-cell simulations of oblique shocks while varying the obliquity and in-plane angles. We show that while the proportion of reflected electrons is negligible for theta (Bn) = 74.degrees 3, it increases to R similar to 5% for theta (Bn) = 30 degrees, and that, via the electron acoustic instability, these electrons power electrostatic waves upstream with energy density proportional to R (0.6) and a wavelength approximate to 2 lambda (se), where lambda (se) is the electron skin length. While the initial reflection mechanism is typically a combination of shock-surfing acceleration and magnetic mirroring, we show that once the electrostatic waves have been generated upstream, they themselves can increase the momenta of upstream electrons parallel to the magnetic field. In less than or similar to 1% of cases, upstream electrons are prematurely turned away from the shock and never injected downstream. In contrast, a similar fraction is rescattered back toward the shock after reflection, reinteracts with the shock with energies much greater than thermal, and crosses into the downstream. Y1 - 2022 U6 - https://doi.org/10.3847/1538-4357/ac69c7 SN - 0004-637X SN - 1538-4357 VL - 931 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Dineva, Ekaterina Ivanova A1 - Pearson, Jeniveve A1 - Ilyin, Ilya A1 - Verma, Meetu A1 - Diercke, Andrea A1 - Strassmeier, Klaus A1 - Denker, Carsten T1 - Characterization of chromospheric activity based on Sun-as-a-star spectral and disk-resolved activity indices JF - Astronomische Nachrichten = Astronomical notes N2 - The strong chromospheric absorption lines Ca ii H & K are tightly connected to stellar surface magnetic fields. Only for the Sun, spectral activity indices can be related to evolving magnetic features on the solar disk. The Solar Disk-Integrated (SDI) telescope feeds the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) of the Large Binocular Telescope (LBT) at Mt. Graham International Observatory, Arizona, U.S.A. We present high-resolution, high-fidelity spectra that were recorded on 184 & 82 days in 2018 & 2019 and derive the Ca ii H & K emission ratio, that is, the S-index. In addition, we compile excess brightness and area indices based on full-disk Ca ii K-line-core filtergrams of the Chromospheric Telescope (ChroTel) at Observatorio del Teide, Tenerife, Spain and full-disk ultraviolet (UV) 1600 angstrom images of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Thus, Sun-as-a-star spectral indices are related to their counterparts derived from resolved images of the solar chromosphere. All indices display signatures of rotational modulation, even during the very low magnetic activity in the minimum of Solar Cycle 24. Bringing together different types of activity indices has the potential to join disparate chromospheric datasets yielding a comprehensive description of chromospheric activity across many solar cycles. KW - astronomical databases KW - miscellaneous KW - methods KW - data analysis KW - activity KW - Sun KW - atmosphere KW - chromosphere KW - techniques KW - spectroscopic Y1 - 2022 U6 - https://doi.org/10.1002/asna.20223996 SN - 0004-6337 SN - 1521-3994 VL - 343 IS - 5 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Willner, Sven N. A1 - Glanemann, Nicole A1 - Levermann, Anders T1 - Investment incentive reduced by climate damages can be restored by optimal policy JF - Nature Communications N2 - Increasing greenhouse gas emissions are likely to impact not only natural systems but economies worldwide. If these impacts alter future economic development, the financial losses will be significantly higher than the mere direct damages. So far, potentially aggravating investment responses were considered negligible. Here we consistently incorporate an empirically derived temperature-growth relation into the simple integrated assessment model DICE. In this framework we show that, if in the next eight decades varying temperatures impact economic growth as has been observed in the past three decades, income is reduced by similar to 20% compared to an economy unaffected by climate change. Hereof similar to 40% are losses due to growth effects of which similar to 50% result from reduced incentive to invest. This additional income loss arises from a reduced incentive for future investment in anticipation of a reduced return and not from an explicit climate protection policy. Under economically optimal climate-change mitigation, however, optimal investment would only be reduced marginally as mitigation efforts keep returns high. Y1 - 2021 U6 - https://doi.org/10.1038/s41467-021-23547-5 SN - 2041-1723 VL - 12 IS - 1 PB - Nature Publishing Group UK CY - London ER - TY - JOUR A1 - Pasemann, Gregor A1 - Flemming, Sven A1 - Alonso, Sergio A1 - Beta, Carsten A1 - Stannat, Wilhelm T1 - Diffusivity estimation for activator-inhibitor models BT - theory and application to intracellular dynamics of the actin cytoskeleton JF - Journal of nonlinear science N2 - A theory for diffusivity estimation for spatially extended activator-inhibitor dynamics modeling the evolution of intracellular signaling networks is developed in the mathematical framework of stochastic reaction-diffusion systems. In order to account for model uncertainties, we extend the results for parameter estimation for semilinear stochastic partial differential equations, as developed in Pasemann and Stannat (Electron J Stat 14(1):547-579, 2020), to the problem of joint estimation of diffusivity and parametrized reaction terms. Our theoretical findings are applied to the estimation of effective diffusivity of signaling components contributing to intracellular dynamics of the actin cytoskeleton in the model organism Dictyostelium discoideum. KW - Parametric drift estimation KW - Stochastic reaction– diffusion KW - systems KW - Maximum likelihood estimation KW - Actin cytoskeleton dynamics Y1 - 2021 U6 - https://doi.org/10.1007/s00332-021-09714-4 SN - 0938-8974 SN - 1432-1467 VL - 31 IS - 3 PB - Springer CY - New York ER - TY - JOUR A1 - Deb, Marwan A1 - Molho, Pierre A1 - Barbara, Bernard T1 - Magnetic damping of ferromagnetic and exchange resonance modes in a ferrimagnetic insulator JF - Physical review : B, Condensed matter and materials physics N2 - Understanding the damping is an important fundamental problem with widespread implications in magnetic technology. Ferrimagnetic materials offer a rich platform to explore not only the damping of the ferromagnetic mode, but also the damping of the high-frequency exchange mode very promising for ultrafast devices. Here we use time-resolved magneto-optical Kerr effect to investigate the ferromagnetic and exchange resonance modes and their damping in the bismuth-doped gadolinium iron garnet over a broad range of magnetic fields (0-10 T) and temperatures (50-300 K) including the magnetization and angular compensation points. These two resonance modes are excited via the inverse Faraday effect and unambiguously identified by their distinct frequency dependence on temperature and magnetic field. The temperature-dependent measurements in the external magnetic field H-ext = 2 T revealed that the intrinsic damping of the ferromagnetic mode is always smaller than the one of the exchange modes and both have a maximum near the angular compensation point. These results are fully consistent with recent predictions of atomistic simulations and a theory based on two-sublattice Landau-Lifshitz-Bloch equation. We also demonstrate that the damping of these modes varies differently as a function of H-ext. We explain the observed behaviors by considering the different features of the effective fields defining the precession frequencies of the ferromagnetic and exchange modes. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevB.105.014432 SN - 2469-9950 SN - 2469-9969 VL - 105 IS - 1 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Schröder, Jakob A1 - Evans, Alexander A1 - Mishurova, Tatiana A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Serrano-Munoz, Itziar A1 - Fritsch, Tobias A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Diffraction-based residual stress characterization in laser additive manufacturing of metals JF - Metals : open access journal N2 - Laser-based additive manufacturing methods allow the production of complex metal structures within a single manufacturing step. However, the localized heat input and the layer-wise manufacturing manner give rise to large thermal gradients. Therefore, large internal stress (IS) during the process (and consequently residual stress (RS) at the end of production) is generated within the parts. This IS or RS can either lead to distortion or cracking during fabrication or in-service part failure, respectively. With this in view, the knowledge on the magnitude and spatial distribution of RS is important to develop strategies for its mitigation. Specifically, diffraction-based methods allow the spatial resolved determination of RS in a non-destructive fashion. In this review, common diffraction-based methods to determine RS in laser-based additive manufactured parts are presented. In fact, the unique microstructures and textures associated to laser-based additive manufacturing processes pose metrological challenges. Based on the literature review, it is recommended to (a) use mechanically relaxed samples measured in several orientations as appropriate strain-free lattice spacing, instead of powder, (b) consider that an appropriate grain-interaction model to calculate diffraction-elastic constants is both material- and texture-dependent and may differ from the conventionally manufactured variant. Further metrological challenges are critically reviewed and future demands in this research field are discussed. KW - laser-based additive manufacturing KW - residual stress analysis KW - X-ray and KW - neutron diffraction KW - diffraction-elastic constants KW - strain-free lattice KW - spacing Y1 - 2021 U6 - https://doi.org/10.3390/met11111830 SN - 2075-4701 VL - 11 IS - 11 PB - MDPI CY - Basel ER - TY - JOUR A1 - Wendt, Martin A1 - Bouche, Nicolas F. A1 - Zabl, Johannes A1 - Schroetter, Ilane A1 - Muzahid, Sowgat T1 - MusE GAs FLOw and Wind V. The dust/metallicity-anisotropy of the circum-galactic medium JF - Monthly notices of the Royal Astronomical Society N2 - We investigate whether the dust content of the circum-galactic medium (CGM) depends on the location of the quasar sightline with respect to the galaxy major-axis using 13 galaxy-Mg II absorber pairs (9-81 kpc distance) from the MusE GAs FLOw and Wind (MEGAFLOW) survey at 0.4 < z < 1.4. The dust content of the CGM is obtained from [Zn/Fe] using ultraviolet and visual echelle spectrograph data. When a direct measurement of [Zn/Fe] is unavailable, we estimate the dust depletion from a method that consists in solving for the depletion from multiple singly ionized ions (e.g. Mn II, Cr II, and Zn II) since each ion depletes on dust grains at different rates. We find a positive correlation between the azimuthal angle and [Zn/Fe] with a Pearson's gamma = 0.70 +/- 0.14. The sightlines along the major axis show [Zn/Fe] < 0.5, whereas the [Zn/Fe] is > 0.8 along the minor axis. These results suggest that the CGM along the minor axis is on average more metal enriched (by approximate to 1 dex) than the gas located along the major axis of galaxies provided that dust depletion is a proxy for metallicity. This anisotropic distribution is consistent with recent results on outflow and accretion in hydro-dynamical simulations. KW - galaxies: evolution KW - galaxies: formation KW - intergalactic medium KW - quasars: KW - absorption lines Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab049 SN - 0035-8711 SN - 1365-2966 VL - 502 IS - 3 SP - 3733 EP - 3745 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Xu, Pengbo A1 - Metzler, Ralf A1 - Wang, Wanli T1 - Infinite density and relaxation for Levy walks in an external potential BT - Hermite polynomial approach JF - Physical review N2 - Levy walks are continuous-time random-walk processes with a spatiotemporal coupling of jump lengths and waiting times. We here apply the Hermite polynomial method to study the behavior of LWs with power-law walking time density for four different cases. First we show that the known result for the infinite density of an unconfined, unbiased LW is consistently recovered. We then derive the asymptotic behavior of the probability density function (PDF) for LWs in a constant force field, and we obtain the corresponding qth-order moments. In a harmonic external potential we derive the relaxation dynamic of the LW. For the case of a Poissonian walking time an exponential relaxation behavior is shown to emerge. Conversely, a power-law decay is obtained when the mean walking time diverges. Finally, we consider the case of an unconfined, unbiased LW with decaying speed v(r ) = v0/./r. When the mean walking time is finite, a universal Gaussian law for the position-PDF of the walker is obtained explicitly. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevE.105.044118 SN - 2470-0045 SN - 2470-0053 VL - 105 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Vinod, Deepak A1 - Aghion, Erez A1 - Sokolov, Igor M. A1 - Metzler, Ralf T1 - Scaled geometric Brownian motion features sub- or superexponential ensemble-averaged, but linear time-averaged mean-squared displacements JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Various mathematical Black-Scholes-Merton-like models of option pricing employ the paradigmatic stochastic process of geometric Brownian motion (GBM). The innate property of such models and of real stock-market prices is the roughly exponential growth of prices with time [on average, in crisis-free times]. We here explore the ensemble- and time averages of a multiplicative-noise stochastic process with power-law-like time-dependent volatility, sigma(t) similar to t(alpha), named scaled GBM (SGBM). For SGBM, the mean-squared displacement (MSD) computed for an ensemble of statistically equivalent trajectories can grow faster than exponentially in time, while the time-averaged MSD (TAMSD)-based on a sliding-window averaging along a single trajectory-is always linear at short lag times Delta. The proportionality factor between these the two averages of the time series is Delta/T at short lag times, where T is the trajectory length, similarly to GBM. This discrepancy of the scaling relations and pronounced nonequivalence of the MSD and TAMSD at Delta/T << 1 is a manifestation of weak ergodicity breaking for standard GBM and for SGBM with s (t)-modulation, the main focus of our analysis. The analytical predictions for the MSD and mean TAMSD for SGBM are in quantitative agreement with the results of stochastic computer simulations. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevE.103.062127 SN - 2470-0045 SN - 2470-0053 VL - 103 IS - 6 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Sparre, Martin A1 - Whittingham, Joseph A1 - Damle, Mitali A1 - Hani, Maan H. A1 - Richter, Philipp A1 - Ellison, Sara L. A1 - Pfrommer, Christoph A1 - Vogelsberger, Mark T1 - Gas flows in galaxy mergers BT - supersonic turbulence in bridges, accretion from the circumgalactic medium, and metallicity dilution JF - Monthly notices of the Royal Astronomical Society N2 - In major galaxy mergers, the orbits of stars are violently perturbed, and gas is torqued to the centre, diluting the gas metallicity and igniting a starburst. In this paper, we study the gas dynamics in and around merging galaxies using a series of cosmological magnetohydrodynamical zoom-in simulations. We find that the gas bridge connecting the merging galaxies pre-coalescence is dominated by turbulent pressure, with turbulent Mach numbers peaking at values of 1.6-3.3. This implies that bridges are dominated by supersonic turbulence, and are thus ideal candidates for studying the impact of extreme environments on star formation. We also find that gas accreted from the circumgalactic medium (CGM) during the merger significantly contributes (27-51 percent) to the star formation rate (SFR) at the time of coalescence and drives the subsequent reignition of star formation in the merger remnant. Indeed, 19-53 percent of the SFR at z = 0 originates from gas belonging to the CGM prior the merger. Finally, we investigate the origin of the metallicity-diluted gas at the centre of merging galaxies. We show that this gas is rapidly accreted on to the Galactic Centre with a time-scale much shorter than that of normal star-forming galaxies. This explains why coalescing galaxies are not well-captured by the fundamental metallicity relation. KW - MHD KW - methods: numerical KW - galaxies: interactions KW - galaxies: starburst Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab3171 SN - 1365-2966 VL - 509 IS - 2 SP - 2720 EP - 2735 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Worseck, Gábor A1 - Khrykin, Ilya Sergeevich A1 - Hennawi, Joseph F. A1 - Prochaska, J. Xavier A1 - Farina, Emanuele Paolo T1 - Dating individual quasars with the He II proximity effect JF - Monthly notices of the Royal Astronomical Society N2 - Constraints on the time-scales of quasar activity are key to understanding the formation and growth of supermassive black holes (SMBHs), quasar triggering mechanisms, and possible feedback effects on their host galaxies. However, observational estimates of this so-called quasar lifetime are highly uncertain (t(Q) similar to 10(4)-10(9) yr), because most methods are indirect and involve many model-dependent assumptions. Direct evidence of earlier activity is gained from the higher ionization state of the intergalactic medium (IGM) in the quasar environs, observable as enhanced Ly alpha transmission in the so-called proximity zone. Due to the similar to 30 Myr equilibration time-scale of He II in the z similar to 3 IGM, the size of the He II proximity zone depends on the time the quasar had been active before our observation t(on) <= t(Q), enabling up to +/- 0.2 dex precise measurements of individual quasar on-times that are comparable to the e-folding time-scale t(S) <= 44 Myr of SMBH growth. Here we present the first statistical sample of 13 quasars whose accurate and precise systemic redshifts allow for measurements of sufficiently precise He II quasar proximity zone sizes between similar or equal to 2 and similar or equal to 15 proper Mpc from science-grade Hubble Space Telescope (HST) spectra. Comparing these sizes to predictions from cosmological hydrodynamical simulations post-processed with 1D radiative transfer, we infer a broad range of quasar on-times from t(on) less than or similar to 1Myr to t(on) > 30 Myr that does not depend on quasar luminosity, black hole mass, or Eddington ratio. These results point to episodic quasar activity over a long duty cycle, but do not rule out substantial SMBH growth during phases of radiative inefficiency or obscuration. KW - intergalactic medium KW - quasars: absorption lines KW - quasars: general KW - quasars: supermassive black holes KW - dark ages, reionization, first stars Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab1685 SN - 0035-8711 SN - 1365-2966 VL - 505 IS - 4 SP - 5084 EP - 5103 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Franović, Igor A1 - Omel'chenko, Oleh A1 - Wolfrum, Matthias T1 - Bumps, chimera states, and Turing patterns in systems of coupled active rotators JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Self-organized coherence-incoherence patterns, called chimera states, have first been reported in systems of Kuramoto oscillators. For coupled excitable units, similar patterns where coherent units are at rest are called bump states. Here, we study bumps in an array of active rotators coupled by nonlocal attraction and global repulsion. We demonstrate how they can emerge in a supercritical scenario from completely coherent Turing patterns: a single incoherent unit appears in a homoclinic bifurcation, undergoing subsequent transitions to quasiperiodic and chaotic behavior, which eventually transforms into extensive chaos with many incoherent units. We present different types of transitions and explain the formation of coherence-incoherence patterns according to the classical paradigm of short-range activation and long-range inhibition. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevE.104.L052201 SN - 2470-0045 SN - 2470-0053 VL - 104 IS - 5 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Vinod, Deepak A1 - Cherstvy, Andrey G. A1 - Wang, Wei A1 - Metzler, Ralf A1 - Sokolov, Igor M. T1 - Nonergodicity of reset geometric Brownian motion JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We derive. the ensemble-and time-averaged mean-squared displacements (MSD, TAMSD) for Poisson-reset geometric Brownian motion (GBM), in agreement with simulations. We find MSD and TAMSD saturation for frequent resetting, quantify the spread of TAMSDs via the ergodicity-breaking parameter and compute distributions of prices. General MSD-TAMSD nonequivalence proves reset GBM nonergodic. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevE.105.L012106 SN - 2470-0045 SN - 2470-0053 VL - 105 IS - 1 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Deb, Marwan A1 - Molho, Pierre A1 - Barbara, Bernard T1 - Tunable exchange-bias-like effect in bi-substituted Gadolinium iron garnet film JF - Physical review applied N2 - Using magneto-optical Faraday and Kerr measurements, we investigate the magnetic and magnetooptical properties of a thick Bi-substituted gadolinium iron garnet film over a broad range of wavelengths (250-850 nm) and temperatures (150-300 K), including the magnetization compensation point, TM. We observe an exchange-bias-like effect in the vicinity of TM. By slightly changing the sample temperature, we can precisely tune the bias field, which reaches a magnitude 6 times higher than the coercive field. We explain this phenomenon by considering the short-range superexchange interaction and a change in the magnetic behavior when moving from the surface to the bulk of the film. This finding may lead to the development of single-film magneto-optical devices based on the exchange-bias effect. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevApplied.15.054064 SN - 2331-7019 VL - 15 IS - 5 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Dörries, Timo A1 - Loos, Sarah Anna Marie A1 - Klapp, Sabine H. L. T1 - Correlation functions of non-Markovian systems out of equilibrium BT - analytical expressions beyond single-exponential memory JF - Journal of statistical mechanics: theory and experiment : JSTAT N2 - This paper is concerned with correlation functions of stochastic systems with memory, a prominent example being a molecule or colloid moving through a complex (e.g. viscoelastic) fluid environment. Analytical investigations of such systems based on non-Markovian stochastic equations are notoriously difficult. A common approximation is that of a single-exponential memory, corresponding to the introduction of one auxiliary variable coupled to the Markovian dynamics of the main variable. As a generalization, we here investigate a class of 'toy' models with altogether three degrees of freedom, giving rise to more complex forms of memory. Specifically, we consider, mainly on an analytical basis, the under- and overdamped motion of a colloidal particle coupled linearly to two auxiliary variables, where the coupling between variables can be either reciprocal or non-reciprocal. Projecting out the auxiliary variables, we obtain non-Markovian Langevin equations with friction kernels and colored noise, whose structure is similar to that of a generalized Langevin equation. For the present systems, however, the non-Markovian equations may violate the fluctuation-dissipation relation as well as detailed balance, indicating that the systems are out of equilibrium. We then study systematically the connection between the coupling topology of the underlying Markovian system and various autocorrelation functions. We demonstrate that already two auxiliary variables can generate surprisingly complex (e.g. non-monotonic or oscillatory) memory and correlation functions. Finally, we show that a minimal overdamped model with two auxiliary variables and suitable non-reciprocal coupling yields correlation functions resembling those describing hydrodynamic backflow in an optical trap. KW - correlation functions KW - memory effects KW - friction Y1 - 2021 U6 - https://doi.org/10.1088/1742-5468/abdead SN - 1742-5468 IS - 3 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Schlemm, Tanja A1 - Feldmann, Johannes A1 - Winkelmann, Ricarda A1 - Levermann, Anders T1 - Stabilizing effect of melange buttressing on the marine ice-cliff instability of the West Antarctic Ice Sheet JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Owing to global warming and particularly high regional ocean warming, both Thwaites and Pine Island Glaciers in the Amundsen region of the Antarctic Ice Sheet could lose their buttressing ice shelves over time. We analyse the possible consequences using the parallel ice sheet model (PISM), applying a simple cliff-calving parameterization and an ice melange-buttressing model. We find that the instantaneous loss of ice-shelf buttressing, due to enforced ice-shelf melting, initiates grounding-line retreat and triggers marine ice sheet instability (MISI). As a consequence, the grounding line progresses into the interior of the West Antarctic Ice Sheet and leads to a sea level contribution of 0.6 m within 100 a. By subjecting the exposed ice cliffs to cliff calving using our simplified parameterization, we also analyse marine ice cliff instability (MICI). In our simulations it can double or even triple the sea level contribution depending on the only loosely constrained parameter that determines the maximum cliff-calving rate. The speed of MICI depends on this upper bound of the calving rate, which is given by the ice melange buttressing the glacier. However, stabilization of MICI may occur for geometric reasons. Because the embayment geometry changes as MICI advances into the interior of the ice sheet, the upper bound on calving rates is reduced and the progress of MICI is slowed down. Although we cannot claim that our simulations bear relevant quantitative estimates of the effect of ice-melange buttressing on MICI, the mechanism has the potential to stop the instability. Further research is needed to evaluate its role for the past and future evolution of the Antarctic Ice Sheet. Y1 - 2022 U6 - https://doi.org/10.5194/tc-16-1979-2022 SN - 1994-0416 SN - 1994-0424 VL - 16 IS - 5 SP - 1979 EP - 1996 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Wang, Suhao A1 - Zuo, Guangzheng A1 - Kim, Jongho A1 - Sirringhaus, Henning T1 - Progress of Conjugated Polymers as Emerging Thermoelectric Materials JF - Progress in polymer science N2 - Thanks to the combined effort s of scientist s in several research fields, the preceding decade has witnessed considerable progress in the use of conjugated polymers as emerging thermoelectric materials leading to significant improvements in performance and demonstration of a number of diverse applications. Despite these recent advances, systematic assessments of the impact of molecular design on thermoelectric properties are scarce. Although several reviews marginally highlight the role of chemical structure, the understanding of structure-performance relationships is still fragmented. An in-depth understanding of the relationship between molecular structure and thermoelectric properties will enable the rational design of next-generation thermoelectric polymers. To this end, this review showcases the state-of-the-art thermoelectric polymers, discusses structure-performance relationships, suggests strategies for improving thermoelectric performance that go beyond molecular design, and highlights some of the most impressive applications of thermoelectric polymers. KW - Organic thermoelectrics KW - Seebeck coefficient KW - Doping KW - Polaron KW - Conducting polymers KW - Structure-performance relationship Y1 - 2022 U6 - https://doi.org/10.1016/j.progpolymsci.2022.101548 SN - 0079-6700 SN - 1873-1619 VL - 129 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ulbricht, Alexander A1 - Mohr, Gunther A1 - Altenburg, Simon J. A1 - Oster, Simon A1 - Maierhofer, Christiane A1 - Bruno, Giovanni T1 - Can potential defects in LPBF be healed from the laser exposure of subsequent layers? BT - A quantitative study JF - Metals : open access journal N2 - Additive manufacturing (AM) of metals and in particular laser powder bed fusion (LPBF) enables a degree of freedom in design unparalleled by conventional subtractive methods. To ensure that the designed precision is matched by the produced LPBF parts, a full understanding of the interaction between the laser and the feedstock powder is needed. It has been shown that the laser also melts subjacent layers of material underneath. This effect plays a key role when designing small cavities or overhanging structures, because, in these cases, the material underneath is feed-stock powder. In this study, we quantify the extension of the melt pool during laser illumination of powder layers and the defect spatial distribution in a cylindrical specimen. During the LPBF process, several layers were intentionally not exposed to the laser beam at various locations, while the build process was monitored by thermography and optical tomography. The cylinder was finally scanned by X-ray computed tomography (XCT). To correlate the positions of the unmolten layers in the part, a staircase was manufactured around the cylinder for easier registration. The results show that healing among layers occurs if a scan strategy is applied, where the orientation of the hatches is changed for each subsequent layer. They also show that small pores and surface roughness of solidified material below a thick layer of unmolten material (>200 mu m) serve as seeding points for larger voids. The orientation of the first two layers fully exposed after a thick layer of unmolten powder shapes the orientation of these voids, created by a lack of fusion. KW - selective laser melting (SLM) KW - additive manufacturing (AM) KW - process KW - monitoring KW - infrared thermography KW - optical tomography KW - X-ray computed KW - tomography (XCT) KW - healing KW - in situ monitoring Y1 - 2021 U6 - https://doi.org/10.3390/met11071012 SN - 2075-4701 VL - 11 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Vilk, Ohad A1 - Campos, Daniel A1 - Méndez, Vicenç A1 - Lourie, Emmanuel A1 - Nathan, Ran A1 - Assaf, Michael T1 - Phase transition in a non-Markovian animal exploration model with preferential returns JF - Physical review letters N2 - We study a non-Markovian and nonstationary model of animal mobility incorporating both exploration and memory in the form of preferential returns. Exact results for the probability of visiting a given number of sites are derived and a practical WKB approximation to treat the nonstationary problem is developed. A mean-field version of this model, first suggested by Song et al., [Modelling the scaling properties of human mobility, Nat. Phys. 6, 818 (2010)] was shown to well describe human movement data. We show that our generalized model adequately describes empirical movement data of Egyptian fruit bats (Rousettus aegyptiacus) when accounting for interindividual variation in the population. We also study the probability of visiting any site a given number of times and derive a mean-field equation. Our analysis yields a remarkable phase transition occurring at preferential returns which scale linearly with past visits. Following empirical evidence, we suggest that this phase transition reflects a trade-off between extensive and intensive foraging modes. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevLett.128.148301 SN - 0031-9007 SN - 1079-7114 VL - 128 IS - 14 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Mattern, Maximilian A1 - Reppert, Alexander von A1 - Zeuschner, Steffen Peer A1 - Pudell, Jan-Etienne A1 - Kühne, F. A1 - Diesing, Detlef A1 - Herzog, Marc A1 - Bargheer, Matias T1 - Electronic energy transport in nanoscale Au/Fe hetero-structures in the perspective of ultrafast lattice dynamics JF - Applied physics letters N2 - We study the ultrafast electronic transport of energy in a photoexcited nanoscale Au/Fe hetero-structure by modeling the spatiotemporal profile of energy densities that drives transient strain, which we quantify by femtosecond x-ray diffraction. This flow of energy is relevant for intrinsic demagnetization and ultrafast spin transport. We measured lattice strain for different Fe layer thicknesses ranging from few atomic layers to several nanometers and modeled the spatiotemporal flow of energy densities. The combination of a high electron-phonon coupling coefficient and a large Sommerfeld constant in Fe is found to yield electronic transfer of nearly all energy from Au to Fe within the first hundreds of femtoseconds. Y1 - 2022 U6 - https://doi.org/10.1063/5.0080378 SN - 0003-6951 SN - 1077-3118 VL - 120 IS - 9 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Ilin, Ekaterina A1 - Poppenhäger, Katja T1 - Searching for flaring star-planet interactions in AU Mic TESS observations JF - Monthly notices of the Royal Astronomical Society N2 - Planets that closely orbit magnetically active stars are thought to be able to interact with their magnetic fields in a way that modulates stellar activity. This modulation in phase with the planetary orbit, such as enhanced X-ray activity, chromospheric spots, radio emission, or flares, is considered the clearest sign of magnetic star-planet interaction (SPI). However, the magnitude of this interaction is poorly constrained, and the intermittent nature of the interaction is a challenge for observers. AU Mic is an early M dwarf, and the most actively flaring planet host detected to date. Its innermost companion, AU Mic b, is a promising target for magnetic SPI observations. We used optical light curves of AU Mic obtained by the Transiting Exoplanet Survey Satellite to search for signs of flaring SPI with AU Mic b using a customized Anderson-Darling test. In the about 50 d of observations, the flare distributions with orbital, rotational, and synodic periods were generally consistent with intrinsic stellar flaring. We found the strongest deviation (p = 0.07, n = 71) from intrinsic flaring with the orbital period of AU Mic b, in the high-energy half of our sample (ED > 1 s). If it reflects the true SPI signal from AU Mic b, extending the observing time by a factor of 2-3 will yield a >3 sigma detection. Continued monitoring of AU Mic may therefore reveal flaring SPI with orbital phase, while rotational modulation will smear out due to the star's strong differential rotation. KW - planets and satellites: individual: AU Mic b KW - planet-star interactions KW - stars: flare KW - stars: individual: AU Mic Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac1232 SN - 0035-8711 SN - 1365-2966 VL - 513 IS - 3 SP - 4579 EP - 4586 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Geier, Stephan A1 - Dorsch, Matti A1 - Pelisoli, Ingrid A1 - Reindl, Nicole A1 - Heber, Ulrich A1 - Irrgang, Andreas T1 - Radial velocity variability and the evolution of hot subdwarf stars JF - Astronomy and astrophysics : an international weekly journal N2 - Hot subdwarf stars represent a late and peculiar stage in the evolution of low-mass stars, since they are likely formed by close binary interactions. In this work, we perform a radial velocity (RV) variability study of a sample of 646 hot subdwarfs with multi-epoch radial velocities based on spectra from Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST). The atmospheric parameters and RVs were taken from the literature. For stars with archival spectra but without literature values, we determined the parameters by fitting model atmospheres. In addition, we redetermined the atmospheric parameters and RVs for all the He-enriched sdO/Bs. This broad sample allowed us to study RV-variability as a function of the location in the T-eff - log g- and T-eff - log n(He)/n(H) diagrams in a statistically significant way. We used the fraction of RV-variable stars and the distribution of the maximum RV variations Delta RVmax as diagnostics. Both indicators turned out to be quite inhomogeneous across the studied parameter ranges. A striking feature is the completely dissimilar behaviour of He-poor and He-rich hot subdwarfs. While the former have a high fraction of close binaries, almost no significant RV variations could be detected for the latter. This has led us to the conclusion that there is likely no evolutionary connection between these subtypes. On the other hand, intermediate He-rich- and extreme He-rich sdOB/Os are more likely to be related. Furthermore, we conclude that the vast majority of this population is formed via one or several binary merger channels. Hot subdwarfs with temperatures cooler than similar to 24 000 K tend to show fewer and smaller RV-variations. These objects might constitute a new subpopulation of binaries with longer periods and late-type or compact companions. The RV-variability properties of the extreme horizontal branch (EHB) and corresponding post-EHB populations of the He-poor hot subdwarfs match and confirm the predicted evolutionary connection between them. Stars found below the canonical EHB at somewhat higher surface gravities show large RV variations and a high RV variability fraction. These properties are consistent with most of them being low-mass EHB stars or progenitors of low-mass helium white dwarfs in close binaries. KW - subdwarfs KW - binaries: spectroscopic KW - stars: horizontal-branch Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202143022 SN - 0004-6361 SN - 1432-0746 VL - 661 PB - EDP Sciences CY - Les Ulis ER -