@misc{SchulzeBettBivouretal.2020,
  author    = {Schulze, Patricia S. C. and Bett, Alexander J. and Bivour, Martin and Caprioglio, Pietro and Gerspacher, Fabian M. and Kabakl{\i}, {\"O}zde Ş. and Richter, Armin and Stolterfoht, Martin and Zhang, Qinxin and Neher, Dieter and Hermle, Martin and Hillebrecht, Harald and Glunz, Stefan W. and Goldschmidt, Jan Christoph},
  title     = {25.1\% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {7},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52566},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525668},
  pages     = {12},
  year      = {2020},
  abstract  = {Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10\% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80\% and up to 25.1\% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3\% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30\% tandem efficiency in the near future.},
  language  = {en}
}
@article{SchulzeBettBivouretal.2020,
  author    = {Schulze, Patricia S. C. and Bett, Alexander J. and Bivour, Martin and Caprioglio, Pietro and Gerspacher, Fabian M. and Kabakl{\i}, {\"O}zde Ş. and Richter, Armin and Stolterfoht, Martin and Zhang, Qinxin and Neher, Dieter and Hermle, Martin and Hillebrecht, Harald and Glunz, Stefan W. and Goldschmidt, Jan Christoph},
  title     = {25.1\% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber},
  series = {Solar RRL},
  volume    = {4},
  journal   = {Solar RRL},
  number    = {7},
  publisher = {John Wiley \& Sons, Inc.},
  address   = {New Jersey},
  pages     = {10},
  year      = {2020},
  abstract  = {Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10\% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80\% and up to 25.1\% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3\% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30\% tandem efficiency in the near future.},
  language  = {en}
}
@article{AssagraAltafimdoCarmoetal.2020,
  author    = {Assagra, Yuri A.O. and Altafim, Ruy Alberto Pisani and do Carmo, Joao P. and Altafim, Ruy A.C. and Rychkov, Dmitry and Wirges, Werner and Gerhard, Reimund},
  title     = {A new route to piezo-polymer transducers: 3D printing of polypropylene ferroelectrets},
  series = {IEEE transactions on dielectrics and electrical insulation},
  volume    = {27},
  journal   = {IEEE transactions on dielectrics and electrical insulation},
  number    = {5},
  publisher = {Inst. of Electr. and Electronics Engineers},
  address   = {Piscataway},
  issn      = {1070-9878},
  doi       = {10.1109/TDEI.2020.008461},
  pages     = {1668 -- 1674},
  year      = {2020},
  abstract  = {Here, a promising approach for producing piezo-polymer transducers in a one-step process is presented. Using 3D-printing technology and polypropylene (PP) filaments, we are able to print a two-layered film structure with regular cavities of precisely controlled size and shape. It is found that the 3D-printed samples exhibit piezoelectric coefficients up to 200 pC/N, similar to those of other PP ferroelectrets, and their temporal and thermal behavior is in good agreement with those known of PP ferroelectrets. The piezoelectric response strongly decreases for applied pressures above 20 kPa, as the pressure in the air-filled cavities strongly influences the overall elastic modulus of ferroelectrets.},
  language  = {en}
}
@article{GomezNavaGrossmannHintscheetal.2020,
  author    = {G{\´o}mez-Nava, Luis and Grossmann, Robert and Hintsche, Marius and Beta, Carsten and Peruani, Fernando},
  title     = {A novel approach to chemotaxis},
  series = {epl : a letters journal exploring the frontiers of physics},
  volume    = {130},
  journal   = {epl : a letters journal exploring the frontiers of physics},
  number    = {6},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0295-5075},
  doi       = {10.1209/0295-5075/130/68002},
  pages     = {7},
  year      = {2020},
  abstract  = {Motivated by the observation of non-exponential run-time distributions of bacterial swimmers, we propose a minimal phenomenological model for taxis of active particles whose motion is controlled by an internal clock. The ticking of the clock depends on an external concentration field, e.g., a chemical substance. We demonstrate that these particles can detect concentration gradients and respond to them by moving up- or down-gradient depending on the clock design, albeit measurements of these fields are purely local in space and instantaneous in time. Altogether, our results open a new route in the study of directional navigation: we show that the use of a clock to control motility actions represents a generic and versatile toolbox to engineer behavioral responses to external cues, such as light, chemical, or temperature gradients.},
  language  = {en}
}
@article{GostkowskaLeknerWallacherGrimmetal.2020,
  author    = {Gostkowska-Lekner, Natalia Katarzyna and Wallacher, Dirk and Grimm, Nico and Habicht, Klaus and Hofmann, Tommy},
  title     = {A novel electrochemical anodization cell for the synthesis of mesoporous silicon},
  series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  volume    = {91},
  journal   = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  number    = {10},
  publisher = {American Institute of Physics},
  address   = {Melville, NY},
  issn      = {0034-6748},
  doi       = {10.1063/5.0008536},
  pages     = {6},
  year      = {2020},
  abstract  = {A novel design of an electrochemical anodization cell dedicated to the synthesis of mesoporous, single-crystalline silicon is presented. First and foremost, the design principle follows user safety since electrochemical etching of silicon requires highly hazardous electrolytes based on hydrofluoric (HF) acid. The novel cell design allows for safe electrolyte handling prior, during, and post-etching. A peristaltic pump with HF-resistant fluoroelastomer tubing transfers electrolytes between dedicated reservoirs and the anodization cell. Due to the flexibility of the cell operation, different processing conditions can be realized providing a large parameter range for the attainable sample thickness, its porosity, and the mean pore size. Rapid etching on the order of several minutes to synthesize micrometer-thick porous silicon epilayers on bulk silicon is possible as well as long-time etching with continuous, controlled electrolyte flow for several days to prepare up to 1000 mu m thick self-supporting porous silicon membranes. A highly adaptable, LabVIEW((TM))-based control software allows for user-defined etching profiles.},
  language  = {en}
}
@article{GrossmannAransonPeruani2020,
  author    = {Großmann, Robert and Aranson, Igor S. and Peruani, Fernando},
  title     = {A particle-field approach bridges phase separation and collective motion in active matter},
  series = {Nature Communications},
  volume    = {11},
  journal   = {Nature Communications},
  number    = {1},
  publisher = {Nature Publishing Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-020-18978-5},
  pages     = {12},
  year      = {2020},
  abstract  = {Whereas self-propelled hard discs undergo motility-induced phase separation, self-propelled rods exhibit a variety of nonequilibrium phenomena, including clustering, collective motion, and spatio-temporal chaos. In this work, we present a theoretical framework representing active particles by continuum fields. This concept combines the simplicity of alignment-based models, enabling analytical studies, and realistic models that incorporate the shape of self-propelled objects explicitly. By varying particle shape from circular to ellipsoidal, we show how nonequilibrium stresses acting among self-propelled rods destabilize motility-induced phase separation and facilitate orientational ordering, thereby connecting the realms of scalar and vectorial active matter. Though the interaction potential is strictly apolar, both, polar and nematic order may emerge and even coexist. Accordingly, the symmetry of ordered states is a dynamical property in active matter. The presented framework may represent various systems including bacterial colonies, cytoskeletal extracts, or shaken granular media. Interacting self-propelled particles exhibit phase separation or collective motion depending on particle shape. A unified theory connecting these paradigms represents a major challenge in active matter, which the authors address here by modeling active particles as continuum fields.},
  language  = {en}
}
@article{SchaffenrothCasewellSchneideretal.2020,
  author    = {Schaffenroth, Veronika and Casewell, Sarah L. and Schneider, D. and Kilkenny, David and Geier, Stephan and Heber, Ulrich and Irrgang, Andreas and Przybilla, Norbert and Marsh, Thomas R. and Littlefair, Stuart P. and Dhillon, Vik S.},
  title     = {A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {501},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {3},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0035-8711},
  doi       = {10.1093/mnras/staa3661},
  pages     = {3847 -- 3870},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{SajediKrivenkovMarchenkoetal.2020,
  author    = {Sajedi, Maryam and Krivenkov, Maxim and Marchenko, Dmitry and Varykhalov, Andrei and Sanchez-Barriga, Jaime and Rienks, Emile D. L. and Rader, Oliver},
  title     = {Absence of a giant Rashba effect in the valence band of lead halide perovskites},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {102},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {8},
  publisher = {American Institute of Physics; American Physical Society (APS)},
  address   = {Woodbury, NY},
  issn      = {2469-9950},
  doi       = {10.1103/PhysRevB.102.081116},
  pages     = {6},
  year      = {2020},
  abstract  = {For hybrid organic-inorganic as well as all-inorganic lead halide perovskites a Rashba effect has been invoked to explain the high efficiency in energy conversion by prohibiting direct recombination. Both a bulk and surface Rashba effect have been predicted. In the valence band of methylammonium (MA) lead bromide a Rashba effect has been reported by angle-resolved photoemission and circular dichroism with giant values of 7-11 eV angstrom. We present band dispersion measurements of MAPbBr(3) and spin-resolved photoemission of CsPbBr3 to show that a large Rashba effect detectable by photoemission or circular dichroism does not exist and cannot be the origin of the high effciency.},
  language  = {en}
}
@article{UmlandtFeldmannSchnecketal.2020,
  author    = {Umlandt, Maren and Feldmann, David and Schneck, Emanuel and Santer, Svetlana and Bekir, Marek},
  title     = {Adsorption of photoresponsive surfactants at solid-liquid interfaces},
  series = {Langmuir},
  volume    = {36},
  journal   = {Langmuir},
  number    = {46},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0743-7463},
  doi       = {10.1021/acs.langmuir.0c02545},
  pages     = {14009 -- 14018},
  year      = {2020},
  abstract  = {We report on the adsorption kinetics of azoben-zene-containing surfactants on solid surfaces of different hydrophobicity. The understanding of this processes is of great importance for many interfacial phenomena that can be actuated and triggered by light, since the surfactant molecules contain a photoresponsive azobenzene group in their hydrophobic tail. Three surfactant types are studied, differing in the spacer connecting the headgroup and the azobenzene unit by between 6 and 10 CH2 groups. Under irradiation with light of a suitable wavelength, the azobenzene undergoes reversible photoisomerization between two states, a nonpolar trans-state and a highly polar cis-state. Consequently, the surfactant molecule changes its hydrophobicity and thus affinity to a surface depending on the photoisomerization state of the azobenzene. The adsorption behavior on hydrophilic (glass) and hydrophobic (TeflonAF) surfaces is analyzed using quartz crystal microbalance with dissipation (QCM-D) and zeta-potential measurements. At equilibrium, the adsorbed surfactant amount is almost twice as large on glass compared to TeflonAF for both isomers. The adsorption rate for the trans-isomers on both surfaces is similar, but the desorption rate of the trans-isomers is faster at the glass-water interface than at the Teflon-water interface. This result demonstrates that the trans-isomers have higher affinity for the glass surface, so the trans-to-cis ratios on glass and TeflonAF are 80/1 and 2/1, respectively, with similar trends for all three surfactant types.},
  language  = {en}
}
@article{EvsevleevPaciornikBruno2020,
  author    = {Evsevleev, Sergei and Paciornik, Sidnei and Bruno, Giovanni},
  title     = {Advanced deep learning-based 3D microstructural characterization of multiphase metal matrix composites},
  series = {Advanced engineering materials},
  volume    = {22},
  journal   = {Advanced engineering materials},
  number    = {4},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1438-1656},
  doi       = {10.1002/adem.201901197},
  pages     = {6},
  year      = {2020},
  abstract  = {The quantitative analysis of microstructural features is a key to understanding the micromechanical behavior of metal matrix composites (MMCs), which is a premise for their use in practice. Herein, a 3D microstructural characterization of a five-phase MMC is performed by synchrotron X-ray computed tomography (SXCT). A workflow for advanced deep learning-based segmentation of all individual phases in SXCT data is shown using a fully convolutional neural network with U-net architecture. High segmentation accuracy is achieved with a small amount of training data. This enables extracting unprecedently precise microstructural parameters (e.g., volume fractions and particle shapes) to be input, e.g., in micromechanical models.},
  language  = {en}
}
@article{PelisoliVosGeieretal.2020,
  author    = {Pelisoli, Ingrid and Vos, Joris and Geier, Stephan and Schaffenroth, Veronika and Baran, Andrzej S.},
  title     = {Alone but not lonely},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {642},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/202038473},
  pages     = {14},
  year      = {2020},
  abstract  = {Context. Hot subdwarfs are core-helium burning stars that show lower masses and higher temperatures than canonical horizontal branch stars. They are believed to be formed when a red giant suffers an extreme mass-loss episode. Binary interaction is suggested to be the main formation channel, but the high fraction of apparently single hot subdwarfs (up to 30\%) has prompted single star formation scenarios to be proposed.Aims. We investigate the possibility that hot subdwarfs could form without interaction by studying wide binary systems. If single formation scenarios were possible, there should be hot subdwarfs in wide binaries that have undergone no interaction.Methods. Angular momentum accretion during interaction is predicted to cause the hot subdwarf companion to spin up to the critical velocity. The effect of this should still be observable given the timescales of the hot subdwarf phase. To study the rotation rates of companions, we have analysed light curves from the Transiting Exoplanet Survey Satellite for all known hot subdwarfs showing composite spectral energy distributions indicating the presence of a main sequence wide binary companion. If formation without interaction were possible, that would also imply the existence of hot subdwarfs in very wide binaries that are not predicted to interact. To identify such systems, we have searched for common proper motion companions with projected orbital distances of up to 0.1 pc to all known spectroscopically confirmed hot subdwarfs using Gaia DR2 astrometry.Results. We find that the companions in composite hot subdwarfs show short rotation periods when compared to field main sequence stars. They display a triangular-shaped distribution with a peak around 2.5 days, similar to what is observed for young open clusters. We also report a shortage of hot subdwarfs with candidate common proper motion companions. We identify only 16 candidates after probing 2938 hot subdwarfs with good astrometry. Out of those, at least six seem to be hierarchical triple systems, in which the hot subdwarf is part of an inner binary.Conclusions. The observed distribution of rotation rates for the companions in known wide hot subdwarf binaries provides evidence of previous interaction causing spin-up. Additionally, there is a shortage of hot subdwarfs in common proper motion pairs, considering the frequency of such systems among progenitors. These results suggest that binary interaction is always required for the formation of hot subdwarfs.},
  language  = {en}
}
@misc{CiemerRehmKurthsetal.2020,
  author    = {Ciemer, Catrin and Rehm, Lars and Kurths, J{\"u}rgen and Donner, Reik Volker and Winkelmann, Ricarda and Boers, Niklas},
  title     = {An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {9},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52586},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525863},
  pages     = {12},
  year      = {2020},
  abstract  = {Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months.},
  language  = {en}
}
@article{CiemerRehmKurthsetal.2020,
  author    = {Ciemer, Catrin and Rehm, Lars and Kurths, J{\"u}rgen and Donner, Reik Volker and Winkelmann, Ricarda and Boers, Niklas},
  title     = {An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures},
  series = {Environmental Research Letters},
  volume    = {15},
  journal   = {Environmental Research Letters},
  number    = {9},
  publisher = {IOP - Institute of Physics Publishing},
  address   = {Bristol},
  pages     = {10},
  year      = {2020},
  abstract  = {Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months.},
  language  = {en}
}
@article{AbdallaAdamAharonianetal.2020,
  author    = {Abdalla, H. and Adam, R. and Aharonian, Felix A. and Benkhali, F. Ait and Ang{\"u}ner, Ekrem Oǧuzhan and Arcaro, C. and Armand, C. and Armstrong, T. and Ashkar, H. and Backes, M. and Baghmanyan, V. and Martins, V. Barbosa and Barnacka, A. and Barnard, M. and Becherini, Y. and Berge, D. and Bernlohr, K. and Bi, B. and Bottcher, M. and Boisson, C. and Bolmont, J. and de Lavergne, M. de Bony and Bordas, Pol and Breuhaus, M. and Brun, F. and Brun, P. and Bryan, M. and Buchele, M. and Bulik, T. and Bylund, T. and Caroff, S. and Carosi, A. and Casanova, Sabrina and Chand, T. and Chandra, S. and Chen, A. and Cotter, G. and Curylo, M. and Mbarubucyeye, J. Damascene and Davids, I. D. and Davies, J. and Deil, C. and Devin, J. and deWilt, P. and Dirson, L. and Djannati-Atai, A. and Dmytriiev, A. and Donath, A. and Doroshenko, V. and Duffy, C. and Dyks, J. and Egberts, Kathrin and Eichhorn, F. and Einecke, S. and Emery, G. and Ernenwein, J. -P. and Feijen, K. and Fegan, S. and Fiasson, A. and de Clairfontaine, G. Fichet and Fontaine, G. and Funk, S. and Fussling, Matthias and Gabici, S. and Gallant, Y. A. and Giavitto, G. and Giunti, L. and Glawion, D. and Glicenstein, J. F. and Gottschall, D. and Grondin, M. -H. and Hahn, J. and Haupt, M. and Hermann, G. and Hinton, J. A. and Hofmann, W. and Hoischen, Clemens and Holch, T. L. and Holler, M. and Horbe, M. and Horns, D. and Huber, D. and Jamrozy, M. and Jankowsky, D. and Jankowsky, F. and Jardin-Blicq, A. and Joshi, V. and Jung-Richardt, I. and Kasai, E. and Kastendieck, M. A. and Katarzynski, K. and Katz, U. and Khangulyan, D. and Khelifi, B. and Klepser, S. and Kluzniak, W. and Komin, Nu. and Konno, R. and Kosack, K. and Kostunin, D. and Kreter, M. and Lamanna, G. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Levy, C. and Lohse, T. and Lypova, I. and Mackey, J. and Majumdar, J. and Malyshev, D. and Malyshev, D. and Marandon, V. and Marchegiani, P. and Marcowith, Alexandre and Mares, A. and Marti-Devesa, G. and Marx, R. and Maurin, G. and Meintjes, P. J. and Meyer, M. and Mitchell, A. and Moderski, R. and Mohamed, M. and Mohrmann, L. and Montanari, A. and Moore, C. and Morris, P. and Moulin, Emmanuel and Muller, J. and Murach, T. and Nakashima, K. and Nayerhoda, A. and de Naurois, M. and Ndiyavala, H. and Niederwanger, F. and Niemiec, J. and Oakes, L. and O'Brien, Patrick and Odaka, H. and Ohm, S. and Olivera-Nieto, L. and Wilhelmi, E. de Ona and Ostrowski, M. and Oya, I. and Panter, M. and Panny, S. and Parsons, R. D. and Peron, G. and Peyaud, B. and Piel, Q. and Pita, S. and Poireau, V. and Noel, A. Priyana and Prokhorov, D. A. and Prokoph, H. and Puhlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Rauth, R. and Reichherzer, P. and Reimer, A. and Reimer, O. and Remy, Q. and Renaud, M. and Rieger, F. and Rinchiuso, L. and Romoli, C. and Rowell, G. and Rudak, B. and Ruiz-Velasco, E. and Sahakian, V. and Sailer, S. and Sanchez, D. A. and Santangelo, Andrea and Sasaki, M. and Scalici, M. and Schussler, F. and Schutte, H. M. and Schwanke, U. and Schwemmer, S. and Seglar-Arroyo, M. and Senniappan, M. and Seyffert, A. S. and Shafi, N. and Shiningayamwe, K. and Simoni, R. and Sinha, A. and Sol, H. and Specovius, A. and Spencer, S. and Spir-Jacob, M. and Stawarz, L. and Sun, L. and Steenkamp, R. and Stegmann, C. and Steinmassl, S. and Steppa, C. and Takahashi, T. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tiziani, D. and Tluczykont, M. and Tomankova, L. and Trichard, C. and Tsirou, M. and Tuffs, R. and Uchiyama, Y. and van der Walt, D. J. and van Eldik, C. and van Rensburg, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Vincent, P. and Vink, J. and Volk, H. J. and Vuillaume, T. and Wadiasingh, Z. and Wagner, S. J. and Watson, J. and Werner, F. and White, R. and Wierzcholska, A. and Wong, Yu Wun and Yusafzai, A. and Zacharias, M. and Zanin, R. and Zargaryan, D. and Zdziarski, A. A. and Zech, Alraune and Zhu, S. J. and Ziegler, A. and Zorn, J. and Zouari, S. and Zywucka, N.},
  title     = {An extreme particle accelerator in the Galactic plane},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {644},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  organization    = {HESS Collaboration},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/202038851},
  pages     = {8},
  year      = {2020},
  abstract  = {The unidentified very-high-energy (VHE; E > 0.1 TeV) gamma -ray source, HESS J1826-130, was discovered with the High Energy Stereoscopic System (HESS) in the Galactic plane. The analysis of 215 h of HESS data has revealed a steady gamma -ray flux from HESS J1826-130, which appears extended with a half-width of 0.21 degrees +/- 0.02 <br /> (stat)degrees <br /> stat degrees +/- 0.05 <br /> (sys)degrees sys degrees . The source spectrum is best fit with either a power-law function with a spectral index Gamma = 1.78 +/- 0.10(stat) +/- 0.20(sys) and an exponential cut-off at 15.2 <br /> (+5.5)(-3.2) -3.2+5.5 TeV, or a broken power-law with Gamma (1) = 1.96 +/- 0.06(stat) +/- 0.20(sys), Gamma (2) = 3.59 +/- 0.69(stat) +/- 0.20(sys) for energies below and above E-br = 11.2 +/- 2.7 TeV, respectively. The VHE flux from HESS J1826-130 is contaminated by the extended emission of the bright, nearby pulsar wind nebula, HESS J1825-137, particularly at the low end of the energy spectrum. Leptonic scenarios for the origin of HESS J1826-130 VHE emission related to PSR J1826-1256 are confronted by our spectral and morphological analysis. In a hadronic framework, taking into account the properties of dense gas regions surrounding HESS J1826-130, the source spectrum would imply an astrophysical object capable of accelerating the parent particle population up to greater than or similar to 200 TeV. Our results are also discussed in a multiwavelength context, accounting for both the presence of nearby supernova remnants, molecular clouds, and counterparts detected in radio, X-rays, and TeV energies.},
  language  = {en}
}
@misc{MunyaevSmirnovKostinetal.2020,
  author    = {Munyaev, Vyacheslav and Smirnov, Lev A. and Kostin, Vasily and Osipov, Grigory V. and Pikovskij, Arkadij},
  title     = {Analytical approach to synchronous states of globally coupled noisy rotators},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {2},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52426},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-524261},
  pages     = {17},
  year      = {2020},
  abstract  = {We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.},
  language  = {en}
}
@article{MunyaevSmirnovKostinetal.2020,
  author    = {Munyaev, Vyacheslav O. and Smirnov, Lev A. and Kostin, Vasily A. and Osipov, Grigory V. and Pikovskij, Arkadij},
  title     = {Analytical approach to synchronous states of globally coupled noisy rotators},
  series = {New journal of physics : the open-access journal for physics},
  volume    = {22},
  journal   = {New journal of physics : the open-access journal for physics},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/ab6f93},
  pages     = {14},
  year      = {2020},
  abstract  = {We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.},
  language  = {en}
}
@article{MunyaevSmirnovKostinetal.2020,
  author    = {Munyaev, Vyacheslav and Smirnov, Lev A. and Kostin, Vasily and Osipov, Grigory V. and Pikovskij, Arkadij},
  title     = {Analytical approach to synchronous states of globally coupled noisy rotators},
  series = {New Journal of Physics},
  volume    = {22},
  journal   = {New Journal of Physics},
  number    = {2},
  publisher = {Springer Science},
  address   = {New York},
  pages     = {15},
  year      = {2020},
  abstract  = {We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.},
  language  = {en}
}
@article{PerdigonToroZhangMarkinaetal.2020,
  author    = {Perdig{\´o}n-Toro, Lorena and Zhang, Huotian and Markina, Anastaa si and Yuan, Jun and Hosseini, Seyed Mehrdad and Wolff, Christian Michael and Zuo, Guangzheng and Stolterfoht, Martin and Zou, Yingping and Gao, Feng and Andrienko, Denis and Shoaee, Safa and Neher, Dieter},
  title     = {Barrierless free charge generation in the high-performance PM6:Y6 bulk heterojunction non-fullerene solar cell},
  series = {Advanced materials},
  volume    = {32},
  journal   = {Advanced materials},
  number    = {9},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0935-9648},
  doi       = {10.1002/adma.201906763},
  pages     = {9},
  year      = {2020},
  abstract  = {Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.},
  language  = {en}
}
@article{EmanuelCherstvyMetzleretal.2020,
  author    = {Emanuel, Marc D. and Cherstvy, Andrey G. and Metzler, Ralf and Gompper, Gerhard},
  title     = {Buckling transitions and soft-phase invasion of two-component icosahedral shells},
  series = {Physical review / publ. by The American Physical Society. E, Statistical, nonlinear, and soft matter physics},
  volume    = {102},
  journal   = {Physical review / publ. by The American Physical Society. E, Statistical, nonlinear, and soft matter physics},
  number    = {6},
  publisher = {Woodbury},
  address   = {New York},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.102.062104},
  pages     = {26},
  year      = {2020},
  abstract  = {What is the optimal distribution of two types of crystalline phases on the surface of icosahedral shells, such as of many viral capsids? We here investigate the distribution of a thin layer of soft material on a crystalline convex icosahedral shell. We demonstrate how the shapes of spherical viruses can be understood from the perspective of elasticity theory of thin two-component shells. We develop a theory of shape transformations of an icosahedral shell upon addition of a softer, but still crystalline, material onto its surface. We show how the soft component "invades" the regions with the highest elastic energy and stress imposed by the 12 topological defects on the surface. We explore the phase diagram as a function of the surface fraction of the soft material, the shell size, and the incommensurability of the elastic moduli of the rigid and soft phases. We find that, as expected, progressive filling of the rigid shell by the soft phase starts from the most deformed regions of the icosahedron. With a progressively increasing soft-phase coverage, the spherical segments of domes are filled first (12 vertices of the shell), then the cylindrical segments connecting the domes (30 edges) are invaded, and, ultimately, the 20 flat faces of the icosahedral shell tend to be occupied by the soft material. We present a detailed theoretical investigation of the first two stages of this invasion process and develop a model of morphological changes of the cone structure that permits noncircular cross sections. In conclusion, we discuss the biological relevance of some structures predicted from our calculations, in particular for the shape of viral capsids.},
  language  = {en}
}
@article{SchulzLieutenantXiaoetal.2020,
  author    = {Schulz, Christian and Lieutenant, Klaus and Xiao, Jie and Hofmann, Tommy and Wong, Deniz and Habicht, Klaus},
  title     = {Characterization of the soft X-ray spectrometer PEAXIS at BESSY II},
  series = {Journal of synchrotron radiation},
  volume    = {27},
  journal   = {Journal of synchrotron radiation},
  publisher = {International Union of Crystallography},
  address   = {Chester},
  issn      = {1600-5775},
  doi       = {10.1107/S1600577519014887},
  pages     = {238 -- 249},
  year      = {2020},
  abstract  = {The performance of the recently commissioned spectrometer PEAXIS for resonant inelastic soft X-ray scattering (RIXS) and X-ray photoelectron spectroscopy and its hosting beamline U41-PEAXIS at the BESSY II synchrotron are characterized. The beamline provides linearly polarized light from 180 eV to 1600 eV allowing for RIXS measurements in the range 200-1200 eV. The monochromator optics can be operated in different configurations to provide either high flux with up to 10(12) photons s(-1) within the focal spot at the sample or high energy resolution with a full width at half maximum of <40 meV at an incident photon energy of similar to 400 eV. The measured total energy resolution of the RIXS spectrometer is in very good agreement with theoretically predicted values obtained by ray-tracing simulations. PEAXIS features a 5 m-long RIXS spectrometer arm that can be continuously rotated about the sample position by 106 degrees within the horizontal photon scattering plane, thus enabling the study of momentum-transfer-dependent excitations. Selected scientific examples are presented to demonstrate the instrument capabilities, including measurements of excitations in single-crystalline NiO and in liquid acetone employing a fluid cell sample manipulator. Planned upgrades of the beamline and the RIXS spectrometer to further increase the energy resolution to similar to 100 meV at 1000 eV incident photon energy are discussed.},
  language  = {en}
}
@misc{SchulzLieutenantXiaoetal.2020,
  author    = {Schulz, Christian and Lieutenant, Klaus and Xiao, Jie and Hofmann, Tommy and Wong, Deniz and Habicht, Klaus},
  title     = {Characterization of the soft X-ray spectrometer PEAXIS at BESSY II},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-54992},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-549928},
  pages     = {14},
  year      = {2020},
  abstract  = {The performance of the recently commissioned spectrometer PEAXIS for resonant inelastic soft X-ray scattering (RIXS) and X-ray photoelectron spectroscopy and its hosting beamline U41-PEAXIS at the BESSY II synchrotron are characterized. The beamline provides linearly polarized light from 180 eV to 1600 eV allowing for RIXS measurements in the range 200-1200 eV. The monochromator optics can be operated in different configurations to provide either high flux with up to 10(12) photons s(-1) within the focal spot at the sample or high energy resolution with a full width at half maximum of <40 meV at an incident photon energy of similar to 400 eV. The measured total energy resolution of the RIXS spectrometer is in very good agreement with theoretically predicted values obtained by ray-tracing simulations. PEAXIS features a 5 m-long RIXS spectrometer arm that can be continuously rotated about the sample position by 106 degrees within the horizontal photon scattering plane, thus enabling the study of momentum-transfer-dependent excitations. Selected scientific examples are presented to demonstrate the instrument capabilities, including measurements of excitations in single-crystalline NiO and in liquid acetone employing a fluid cell sample manipulator. Planned upgrades of the beamline and the RIXS spectrometer to further increase the energy resolution to similar to 100 meV at 1000 eV incident photon energy are discussed.},
  language  = {en}
}
@article{ErlerRiebeBeitzetal.2020,
  author    = {Erler, Alexander and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Grothusheitkamp, Daniela and Kunz, Thomas and Methner, Frank-J{\"u}rgen},
  title     = {Characterization of volatile metabolites formed by molds on barley by mass and ion mobility spectrometry},
  series = {Journal of mass spectrometr},
  volume    = {55},
  journal   = {Journal of mass spectrometr},
  number    = {5},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {1076-5174},
  doi       = {10.1002/jms.4501},
  pages     = {1 -- 10},
  year      = {2020},
  abstract  = {The contamination of barley by molds on the field or in storage leads to the spoilage of grain and the production of mycotoxins, which causes major economic losses in malting facilities and breweries. Therefore, on-site detection of hidden fungus contaminations in grain storages based on the detection of volatile marker compounds is of high interest. In this work, the volatile metabolites of 10 different fungus species are identified by gas chromatography (GC) combined with two complementary mass spectrometric methods, namely, electron impact (EI) and chemical ionization at atmospheric pressure (APCI)-mass spectrometry (MS). The APCI source utilizes soft X-radiation, which enables the selective protonation of the volatile metabolites largely without side reactions. Nearly 80 volatile or semivolatile compounds from different substance classes, namely, alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, alkenes, terpenes, oxidized terpenes, sesquiterpenes, and oxidized sesquiterpenes, could be identified. The profiles of volatile and semivolatile metabolites of the different fungus species are characteristic of them and allow their safe differentiation. The application of the same GC parameters and APCI source allows a simple method transfer from MS to ion mobility spectrometry (IMS), which permits on-site analyses of grain stores. Characterization of IMS yields limits of detection very similar to those of APCI-MS. Accordingly, more than 90\% of the volatile metabolites found by APCI-MS were also detected in IMS. In addition to different fungus genera, different species of one fungus genus could also be differentiated by GC-IMS.},
  language  = {en}
}
@misc{AlirezaeizanjaniGrossmannPfeiferetal.2020,
  author    = {Alirezaeizanjani, Zahra and Großmann, Robert and Pfeifer, Veronika and Hintsche, Marius and Beta, Carsten},
  title     = {Chemotaxis strategies of bacteria with multiple run modes},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {22},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51909},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-519098},
  pages     = {10},
  year      = {2020},
  abstract  = {Bacterial chemotaxis-a fundamental example of directional navigation in the living world-is key to many biological processes, including the spreading of bacterial infections. Many bacterial species were recently reported to exhibit several distinct swimming modes-the flagella may, for example, push the cell body or wrap around it. How do the different run modes shape the chemotaxis strategy of a multimode swimmer? Here, we investigate chemotactic motion of the soil bacterium Pseudomonas putida as a model organism. By simultaneously tracking the position of the cell body and the configuration of its flagella, we demonstrate that individual run modes show different chemotactic responses in nutrition gradients and, thus, constitute distinct behavioral states. On the basis of an active particle model, we demonstrate that switching between multiple run states that differ in their speed and responsiveness provides the basis for robust and efficient chemotaxis in complex natural habitats.},
  language  = {en}
}
@article{AlirezaeizanjaniGrossmannPfeiferetal.2020,
  author    = {Alirezaeizanjani, Zahra and Großmann, Robert and Pfeifer, Veronika and Hintsche, Marius and Beta, Carsten},
  title     = {Chemotaxis strategies of bacteria with multiple run modes},
  series = {Science advances},
  volume    = {6},
  journal   = {Science advances},
  number    = {22},
  publisher = {American Association for the Advancement of Science},
  address   = {Washington},
  issn      = {2375-2548},
  doi       = {10.1126/sciadv.aaz6153},
  pages     = {8},
  year      = {2020},
  abstract  = {Bacterial chemotaxis-a fundamental example of directional navigation in the living world-is key to many biological processes, including the spreading of bacterial infections. Many bacterial species were recently reported to exhibit several distinct swimming modes-the flagella may, for example, push the cell body or wrap around it. How do the different run modes shape the chemotaxis strategy of a multimode swimmer? Here, we investigate chemotactic motion of the soil bacterium Pseudomonas putida as a model organism. By simultaneously tracking the position of the cell body and the configuration of its flagella, we demonstrate that individual run modes show different chemotactic responses in nutrition gradients and, thus, constitute distinct behavioral states. On the basis of an active particle model, we demonstrate that switching between multiple run states that differ in their speed and responsiveness provides the basis for robust and efficient chemotaxis in complex natural habitats.},
  language  = {en}
}
@article{MarschallSkorovZakharovetal.2020,
  author    = {Marschall, Raphael and Skorov, Yuri and Zakharov, Vladimir and Rezac, Ladislav and Gerig, Selina-Barbara and Christou, Chariton and Dadzie, S. Kokou and Migliorini, Alessandra and Rinaldi, Giovanna and Agarwal, Jessica and Vincent, Jean-Baptiste and Kappel, David},
  title     = {Cometary comae-surface links the physics of gas and dust from the surface to a spacecraft},
  series = {Space science reviews},
  volume    = {216},
  journal   = {Space science reviews},
  number    = {8},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0038-6308},
  doi       = {10.1007/s11214-020-00744-0},
  pages     = {53},
  year      = {2020},
  abstract  = {A comet is a highly dynamic object, undergoing a permanent state of change. These changes have to be carefully classified and considered according to their intrinsic temporal and spatial scales. The Rosetta mission has, through its contiguous in-situ and remote sensing coverage of comet 67P/Churyumov-Gerasimenko (hereafter 67P) over the time span of August 2014 to September 2016, monitored the emergence, culmination, and winding down of the gas and dust comae. This provided an unprecedented data set and has spurred a large effort to connect in-situ and remote sensing measurements to the surface. In this review, we address our current understanding of cometary activity and the challenges involved when linking comae data to the surface. We give the current state of research by describing what we know about the physical processes involved from the surface to a few tens of kilometres above it with respect to the gas and dust emission from cometary nuclei. Further, we describe how complex multidimensional cometary gas and dust models have developed from the Halley encounter of 1986 to today. This includes the study of inhomogeneous outgassing and determination of the gas and dust production rates. Additionally, the different approaches used and results obtained to link coma data to the surface will be discussed. We discuss forward and inversion models and we describe the limitations of the respective approaches. The current literature suggests that there does not seem to be a single uniform process behind cometary activity. Rather, activity seems to be the consequence of a variety of erosion processes, including the sublimation of both water ice and more volatile material, but possibly also more exotic processes such as fracture and cliff erosion under thermal and mechanical stress, sub-surface heat storage, and a complex interplay of these processes. Seasons and the nucleus shape are key factors for the distribution and temporal evolution of activity and imply that the heliocentric evolution of activity can be highly individual for every comet, and generalisations can be misleading.},
  language  = {en}
}
@article{KurilovichMantsevichStevensonetal.2020,
  author    = {Kurilovich, Aleksandr A. and Mantsevich, Vladimir and Stevenson, Keith J. and Chechkin, Aleksei V. and Palyulin, V. V.},
  title     = {Complex diffusion-based kinetics of photoluminescence in semiconductor nanoplatelets},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {22},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {42},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/d0cp03744c},
  pages     = {24686 -- 24696},
  year      = {2020},
  abstract  = {We present a diffusion-based simulation and theoretical models for explanation of the photoluminescence (PL) emission intensity in semiconductor nanoplatelets. It is shown that the shape of the PL intensity curves can be reproduced by the interplay of recombination, diffusion and trapping of excitons. The emission intensity at short times is purely exponential and is defined by recombination. At long times, it is governed by the release of excitons from surface traps and is characterized by a power-law tail. We show that the crossover from one limit to another is controlled by diffusion properties. This intermediate region exhibits a rich behaviour depending on the value of diffusivity. The proposed approach reproduces all the features of experimental curves measured for different nanoplatelet systems.},
  language  = {en}
}
@article{SamajdarDietrich2020,
  author    = {Samajdar, Anuradha and Dietrich, Tim},
  title     = {Constructing Love-Q relations with gravitational wave detections},
  series = {Physical review : D, Particles, fields, gravitation, and cosmology},
  volume    = {101},
  journal   = {Physical review : D, Particles, fields, gravitation, and cosmology},
  number    = {12},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1550-7998},
  doi       = {10.1103/PhysRevD.101.124014},
  pages     = {6},
  year      = {2020},
  abstract  = {Quasiuniversal relations between the tidal deformability and the quadrupole moment of neutron stars are predicted by theoretical computations, but have not been measured experimentally. We simulate 120 binary neutron star sources and find that Advanced LIGO and Advanced Virgo at design sensitivity could find possible deviations from predicted relations if the neutron stars are highly spinning. A network of envisaged third generation detectors will even allow extracting such relations, providing new tests of general relativity and nuclear physics predictions.},
  language  = {en}
}
@misc{GranadoAbadMetzleretal.2020,
  author    = {Granado, Felipe Le Vot and Abad, Enrique and Metzler, Ralf and Yuste, Santos B.},
  title     = {Continuous time random walk in a velocity field},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1005},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-47999},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-479997},
  pages     = {28},
  year      = {2020},
  abstract  = {We consider the emerging dynamics of a separable continuous time random walk (CTRW) in the case when the random walker is biased by a velocity field in a uniformly growing domain. Concrete examples for such domains include growing biological cells or lipid vesicles, biofilms and tissues, but also macroscopic systems such as expanding aquifers during rainy periods, or the expanding Universe. The CTRW in this study can be subdiffusive, normal diffusive or superdiffusive, including the particular case of a L{\´e}vy flight. We first consider the case when the velocity field is absent. In the subdiffusive case, we reveal an interesting time dependence of the kurtosis of the particle probability density function. In particular, for a suitable parameter choice, we find that the propagator, which is fat tailed at short times, may cross over to a Gaussian-like propagator. We subsequently incorporate the effect of the velocity field and derive a bi-fractional diffusion-advection equation encoding the time evolution of the particle distribution. We apply this equation to study the mixing kinetics of two diffusing pulses, whose peaks move towards each other under the action of velocity fields acting in opposite directions. This deterministic motion of the peaks, together with the diffusive spreading of each pulse, tends to increase particle mixing, thereby counteracting the peak separation induced by the domain growth. As a result of this competition, different regimes of mixing arise. In the case of L{\´e}vy flights, apart from the non-mixing regime, one has two different mixing regimes in the long-time limit, depending on the exact parameter choice: in one of these regimes, mixing is mainly driven by diffusive spreading, while in the other mixing is controlled by the velocity fields acting on each pulse. Possible implications for encounter-controlled reactions in real systems are discussed.},
  language  = {en}
}
@article{GranadoAbadMetzleretal.2020,
  author    = {Granado, Felipe Le Vot and Abad, Enrique and Metzler, Ralf and Yuste, Santos B.},
  title     = {Continuous time random walk in a velocity field},
  series = {New Journal of Physics},
  volume    = {22},
  journal   = {New Journal of Physics},
  publisher = {Dt. Physikalische Ges.},
  address   = {Bad Honnef},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/ab9ae2},
  pages     = {27},
  year      = {2020},
  abstract  = {We consider the emerging dynamics of a separable continuous time random walk (CTRW) in the case when the random walker is biased by a velocity field in a uniformly growing domain. Concrete examples for such domains include growing biological cells or lipid vesicles, biofilms and tissues, but also macroscopic systems such as expanding aquifers during rainy periods, or the expanding Universe. The CTRW in this study can be subdiffusive, normal diffusive or superdiffusive, including the particular case of a L{\´e}vy flight. We first consider the case when the velocity field is absent. In the subdiffusive case, we reveal an interesting time dependence of the kurtosis of the particle probability density function. In particular, for a suitable parameter choice, we find that the propagator, which is fat tailed at short times, may cross over to a Gaussian-like propagator. We subsequently incorporate the effect of the velocity field and derive a bi-fractional diffusion-advection equation encoding the time evolution of the particle distribution. We apply this equation to study the mixing kinetics of two diffusing pulses, whose peaks move towards each other under the action of velocity fields acting in opposite directions. This deterministic motion of the peaks, together with the diffusive spreading of each pulse, tends to increase particle mixing, thereby counteracting the peak separation induced by the domain growth. As a result of this competition, different regimes of mixing arise. In the case of L{\´e}vy flights, apart from the non-mixing regime, one has two different mixing regimes in the long-time limit, depending on the exact parameter choice: in one of these regimes, mixing is mainly driven by diffusive spreading, while in the other mixing is controlled by the velocity fields acting on each pulse. Possible implications for encounter-controlled reactions in real systems are discussed.},
  language  = {en}
}
@article{Rosenblum2020,
  author    = {Rosenblum, Michael},
  title     = {Controlling collective synchrony in oscillatory ensembles by precisely timed pulses},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {30},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {9},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {1054-1500},
  doi       = {10.1063/5.0019823},
  pages     = {9},
  year      = {2020},
  abstract  = {We present an efficient technique for control of synchrony in a globally coupled ensemble by pulsatile action. We assume that we can observe the collective oscillation and can stimulate all elements of the ensemble simultaneously. We pay special attention to the minimization of intervention into the system. The key idea is to stimulate only at the most sensitive phase. To find this phase, we implement an adaptive feedback control. Estimating the instantaneous phase of the collective mode on the fly, we achieve efficient suppression using a few pulses per oscillatory cycle. We discuss the possible relevance of the results for neuroscience, namely, for the development of advanced algorithms for deep brain stimulation, a medical technique used to treat Parkinson's disease.},
  language  = {en}
}
@phdthesis{Mandal2020,
  author    = {Mandal, Partha Sarathi},
  title     = {Controlling the surface band gap in topological states of matter},
  doi       = {10.25932/publishup-48045},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-480459},
  school      = {Universit{\"a}t Potsdam},
  pages     = {122},
  year      = {2020},
  abstract  = {In the present study, we employ the angle-resolved photoemission spectroscopy (ARPES) technique to study the electronic structure of topological states of matter. In particular, the so-called topological crystalline insulators (TCIs) Pb1-xSnxSe and Pb1-xSnxTe, and the Mn-doped Z2 topological insulators (TIs) Bi2Te3 and Bi2Se3. The Z2 class of strong topological insulators is protected by time-reversal symmetry and is characterized by an odd number of metallic Dirac type surface states in the surface Brillouin zone. The topological crystalline insulators on the other hand are protected by the individual crystal symmetries and exhibit an even number of Dirac cones. The topological properties of the lead tin chalcogenides topological crystalline insulators can be tuned by temperature and composition. Here, we demonstrate that Bi-doping of the Pb1-xSnxSe(111) epilayers induces a quantum phase transition from a topological crystalline insulator to a Z2 topological insulator. This occurs because Bi-doping lifts the fourfold valley degeneracy in the bulk. As a consequence a gap appears at ⌈¯, while the three Dirac cones at the M̅ points of the surface Brillouin zone remain intact. We interpret this new phase transition is caused by lattice distortion. Our findings extend the topological phase diagram enormously and make strong topological insulators switchable by distortions or electric field. In contrast, the bulk Bi doping of epitaxial Pb1-xSnxTe(111) films induces a giant Rashba splitting at the surface that can be tuned by the doping level. Tight binding calculations identify their origin as Fermi level pinning by trap states at the surface. Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE) which provide quantized edge states for lossless charge transport applications. The edge states are hosted by a magnetic energy gap at the Dirac point which has not been experimentally observed to date. Our low temperature ARPES studies unambiguously reveal the magnetic gap of Mn-doped Bi2Te3. Our analysis shows a five times larger gap size below the Tc than theoretically predicted. We assign this enhancement to a remarkable structure modification induced by Mn doping. Instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3quintuple layers is formed. This enhances the wave-function overlap and gives rise to a large magnetic gap. Mn-doped Bi2Se3 forms similar heterostructure, but only a nonmagnetic gap is observed in this system. This correlates with the difference in magnetic anisotropy due to the much larger spin-orbit interaction in Bi2Te3 compared to Bi2Se3. These findings provide crucial insights for pushing lossless transport in topological insulators towards room-temperature applications.},
  language  = {en}
}
@article{VinkeGabryschPaolettietal.2020,
  author    = {Vinke, Kira and Gabrysch, Sabine and Paoletti, Emanuela and Rockstr{\"o}m, Johan and Schellnhuber, Hans Joachim},
  title     = {Corona and the climate},
  series = {Global sustainability},
  volume    = {3},
  journal   = {Global sustainability},
  publisher = {Cambridge Univ. Press},
  address   = {Cambridge},
  issn      = {2059-4798},
  doi       = {10.1017/sus.2020.20},
  pages     = {7},
  year      = {2020},
  abstract  = {Lessons from the corona crisis can help manage the even more daunting challenge of anthropogenic global warming.},
  language  = {en}
}
@misc{WolffCanilRehermannetal.2020,
  author    = {Wolff, Christian Michael and Canil, Laura and Rehermann, Carolin and Nguyen, Ngoc Linh and Zu, Fengshuo and Ralaiarisoa, Maryline and Caprioglio, Pietro and Fiedler, Lukas and Stolterfoht, Martin and Kogikoski, Junior, Sergio and Bald, Ilko and Koch, Norbert and Unger, Eva L. and Dittrich, Thomas and Abate, Antonio and Neher, Dieter},
  title     = {Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445-1456)},
  series = {ACS nano},
  volume    = {14},
  journal   = {ACS nano},
  number    = {11},
  publisher = {American Chemical Society},
  address   = {Washington, DC},
  issn      = {1936-0851},
  doi       = {10.1021/acsnano.0c08081},
  pages     = {16156 -- 16156},
  year      = {2020},
  language  = {en}
}
@article{GongToenjesPikovsky2020,
  author    = {Gong, Chen Chris and T{\"o}njes, Ralf and Pikovsky, Arkady},
  title     = {Coupled M{\"o}bius maps as a tool to model Kuramoto phase synchronization},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {102},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  number    = {2},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.102.022206},
  pages     = {12},
  year      = {2020},
  abstract  = {We propose Mobius maps as a tool to model synchronization phenomena in coupled phase oscillators. Not only does the map provide fast computation of phase synchronization, it also reflects the underlying group structure of the sinusoidally coupled continuous phase dynamics. We study map versions of various known continuous-time collective dynamics, such as the synchronization transition in the Kuramoto-Sakaguchi model of nonidentical oscillators, chimeras in two coupled populations of identical phase oscillators, and Kuramoto-Battogtokh chimeras on a ring, and demonstrate similarities and differences between the iterated map models and their known continuous-time counterparts.},
  language  = {en}
}
@article{CaetanoCarvalhoMetzleretal.2020,
  author    = {Caetano, Daniel L. Z. and Carvalho, Sidney Jurado de and Metzler, Ralf and Cherstvy, Andrey G.},
  title     = {Critical adsorption of multiple polyelectrolytes onto a nanosphere},
  series = {Interface : journal of the Royal Society},
  volume    = {17},
  journal   = {Interface : journal of the Royal Society},
  number    = {167},
  publisher = {Royal Society},
  address   = {London},
  issn      = {1742-5689},
  doi       = {10.1098/rsif.2020.0199},
  pages     = {10},
  year      = {2020},
  abstract  = {Employing extensive Monte Carlo computer simulations, we investigate in detail the properties of multichain adsorption of charged flexible polyelectrolytes (PEs) onto oppositely charged spherical nanoparticles (SNPs). We quantify the conditions of critical adsorption-the phase-separation curve between the adsorbed and desorbed states of the PEs-as a function of the SNP surface-charge density and the concentration of added salt. We study the degree of fluctuations of the PE-SNP electrostatic binding energy, which we use to quantify the emergence of the phase subtransitions, including a series of partially adsorbed PE configurations. We demonstrate how the phase-separation adsorption-desorption boundary shifts and splits into multiple subtransitions at low-salt conditions, thereby generalizing and extending the results for critical adsorption of a single PE onto the SNP. The current findings are relevant for finite concentrations of PEs around the attracting SNP, such as the conditions for PE adsorption onto globular proteins carrying opposite electric charges.},
  language  = {en}
}
@article{AwadMetzler2020,
  author    = {Awad, Emad and Metzler, Ralf},
  title     = {Crossover dynamics from superdiffusion to subdiffusion},
  series = {Fractional calculus and applied analysis : an international journal for theory and applications},
  volume    = {23},
  journal   = {Fractional calculus and applied analysis : an international journal for theory and applications},
  number    = {1},
  publisher = {De Gruyter},
  address   = {Berlin ; Boston},
  issn      = {1311-0454},
  doi       = {10.1515/fca-2020-0003},
  pages     = {55 -- 102},
  year      = {2020},
  abstract  = {The Cattaneo or telegrapher's equation describes the crossover from initial ballistic to normal diffusion. Here we study and survey time-fractional generalisations of this equation that are shown to produce the crossover of the mean squared displacement from superdiffusion to subdiffusion. Conditional solutions are derived in terms of Fox H-functions and the dth-order moments as well as the diffusive flux of the different models are derived. Moreover, the concept of the distribution-like is proposed as an alternative to the probability density function.},
  language  = {en}
}
@article{MishurovaBrunoEvsevleevetal.2020,
  author    = {Mishurova, Tatiana and Bruno, Giovanni and Evsevleev, Sergei and Sevostianov, Igor},
  title     = {Determination of macroscopic stress from diffraction experiments},
  series = {Journal of applied physics},
  volume    = {128},
  journal   = {Journal of applied physics},
  number    = {2},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-8979},
  doi       = {10.1063/5.0009101},
  pages     = {14},
  year      = {2020},
  abstract  = {The paper is motivated by some inconsistencies and contradictions present in the literature on the calculation of the so-called diffraction elastic constants. In an attempt at unifying the views that the two communities of Materials Science and Mechanics of Materials have on the subject, we revisit and define the terminology used in the field. We also clarify the limitations of the commonly used approaches and show that a unified methodology is also applicable to textured materials with a nearly arbitrary grain shape. We finally compare the predictions based on this methodology with experimental data obtained by in situ synchrotron radiation diffraction on additively manufactured Ti-6Al-4V alloy. We show that (a) the transverse isotropy of the material yields good agreement between the best-fit isotropy approximation (equivalent to the classic Kroner's model) and the experimental data and (b) the use of a general framework allows the calculation of all components of the tensor of diffraction elastic constants, which are not easily measurable by diffraction methods. This allows us to extend the current state-of-the-art with a predictive tool.},
  language  = {en}
}
@article{QiuBenjaminRamanVenkatesanetal.2020,
  author    = {Qiu, Xunlin and Benjamin, Aravindan Joseph and Raman Venkatesan, Thulasinath and Schmidt, Georg C. and Soler, Ricardo Alonso Quintana and Panicker, Pramul Muraleedhara and Gerhard, Reimund and H{\"u}bler, Arved Carl},
  title     = {Dielectric and electroacoustic assessment of screen-printed piezoelectric polymer layers as flexible transducers},
  series = {IEEE transactions on dielectrics and electrical insulation},
  volume    = {27},
  journal   = {IEEE transactions on dielectrics and electrical insulation},
  number    = {5},
  publisher = {Institute of Electrical and Electronics Engineers},
  address   = {New York, NY},
  issn      = {1070-9878},
  doi       = {10.1109/TDEI.2020.008864},
  pages     = {1683 -- 1690},
  year      = {2020},
  abstract  = {Here, piezoelectric transducers consisting of a P(VDF-TrFE) layer with either silver or PEDOT:PSS screen-printed electrodes are studied. The influence of electrodes on the dielectric and electroacoustic properties are studied in dielectric-spectroscopy and ferroelectric-hysteresis measurements. Only when both the bottom and the top electrodes are made of silver, the typical dielectric relaxation of the P(VDF-TrFE) layer is clearly observed. When one or two of the electrodes are of PEDOT:PSS, a Debye-like relaxation is present. Compared with silver electrodes, PEDOT:PSS electrodes allow for moderate self-healing. Consequently, samples with bottom and top PEDOT:PSS electrodes can be poled to saturation, while samples with silver electrodes can hardly be poled to saturation due to destructive electric breakdown. Acoustic transducer measurements show that silver electrodes facilitate higher and broader frequency operation, while PEDOT:PSS electrodes bring slightly lower total harmonic distortion. Overall, the acoustic performance shows no significant deviations between differently electroded samples so that silver electrodes do not offer any advantages for the transducers studied here due to their much higher tendency for destructive electric breakdown.},
  language  = {en}
}
@article{KosztolowiczMetzler2020,
  author    = {Kosztolowicz, Tadeusz and Metzler, Ralf},
  title     = {Diffusion of antibiotics through a biofilm in the presence of diffusion and absorption barriers},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {102},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  number    = {3},
  publisher = {American Physical Society},
  address   = {Melville, NY},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.102.032408},
  pages     = {11},
  year      = {2020},
  abstract  = {We propose a model of antibiotic diffusion through a bacterial biofilm when diffusion and/or absorption barriers develop in the biofilm. The idea of this model is: We deduce details of the diffusion process in a medium in which direct experimental study is difficult, based on probing diffusion in external regions. Since a biofilm has a gel-like consistency, we suppose that subdiffusion of particles in the biofilm may occur. To describe this process we use a fractional subdiffusion-absorption equation with an adjustable anomalous diffusion exponent. The boundary conditions at the boundaries of the biofilm are derived by means of a particle random walk model on a discrete lattice leading to an expression involving a fractional time derivative. We show that the temporal evolution of the total amount of substance that has diffused through the biofilm explicitly depends on whether there is antibiotic absorption in the biofilm. This fact is used to experimentally check for antibiotic absorption in the biofilm and if subdiffusion and absorption parameters of the biofilm change over time. We propose a four-stage model of antibiotic diffusion in biofilm based on the following physical characteristics: whether there is absorption of the antibiotic in the biofilm and whether all biofilm parameters remain unchanged over time. The biological interpretation of the stages, in particular their relation with the bacterial defense mechanisms, is discussed. Theoretical results are compared with empirical results of ciprofloxacin diffusion through Pseudomonas aeruginosa biofilm, and ciprofloxacin and gentamicin diffusion through Proteus mirabilis biofilm.},
  language  = {en}
}
@article{MagkosKupschBruno2020,
  author    = {Magkos, Sotirios and Kupsch, Andreas and Bruno, Giovanni},
  title     = {Direct iterative reconstruction of computed tomography trajectories reconstruction from limited number of projections with DIRECTT},
  series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  volume    = {91},
  journal   = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  number    = {10},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0034-6748},
  doi       = {10.1063/5.0013111},
  pages     = {8},
  year      = {2020},
  abstract  = {X-ray computed tomography has many applications in materials science and non-destructive testing. While the standard filtered back-projection reconstruction of the radiographic datasets is fast and simple, it typically fails in returning accurate results from missing or inconsistent projections. Among the alternative techniques that have been proposed to handle such data is the Direct Iterative REconstruction of Computed Tomography Trajectories (DIRECTT) algorithm. We describe a new approach to the algorithm, which significantly decreases the computational time while achieving a better reconstruction quality than that of other established algorithms.},
  language  = {en}
}
@article{Bouakline2020,
  author    = {Bouakline, Foudhil},
  title     = {Does nuclear permutation symmetry allow dynamical localization in symmetric double-well achiral molecules?},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {152},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {24},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.5141746},
  pages     = {17},
  year      = {2020},
  abstract  = {We discuss the effect of molecular symmetry on coherent tunneling in symmetric double-well potentials whose two molecular equilibrium configurations are interconverted by nuclear permutations. This is illustrated with vibrational tunneling in ammonia molecules, electronic tunneling in the dihydrogen cation, and laser-induced rotational tunneling of homonuclear diatomics. In this contribution, we reexamine the textbook picture of coherent tunneling in such potentials, which is depicted with a wavepacket shuttling back and forth between the two potential-wells. We show that the common application of this picture to the aforementioned molecules contravenes the principle of the indistinguishability of identical particles. This conflict originates from the sole consideration of the dynamics of the tunneling-mode, connecting the double-well energy minima, and complete omission of all the remaining molecular degrees of freedom. This gives rise to double-well wavepackets that are nonsymmetric under nuclear permutations. To obey quantum statistics, we show that the double-well eigenstates composing these wavepackets must be entangled with the wavefunctions that describe all the omitted molecular modes. These wavefunctions have compensating and opposite nuclear permutation symmetry. This in turn leads to complete quenching of interference effects behind localization in one potential-well or another. Indeed, we demonstrate that the reduced density of probability of the symmetrized molecular wavefunction, where all the molecular coordinates but the tunneling-mode are integrated out, is symmetrically distributed over the two potential-wells, at all times. This applies to any multilevel wavepacket of isotropic or fully aligned symmetric double-well achiral molecules. However, in the case of coherent electronic or vibrational tunneling, fully aligned molecules may exhibit dynamical localization in the space-fixed frame, where the tunneling-mode density shuttles between the opposite directions of the alignment axis. This dynamical spatial-localization results from linear combinations of molecular states that have opposite parity. In summary, this study shows that dynamical localization of the tunneling-mode density on either of the two indistinguishable molecular equilibrium configurations of symmetric double-well achiral molecules is forbidden by quantum statistics, whereas its dynamical localization in the space-fixed frame is allowed by parity. The subtle distinction between these two types of localization has far-reaching implications in the interpretation of many ultrafast molecular dynamics experiments.},
  language  = {en}
}
@article{MejiaMonasterioMetzlerVollmer2020,
  author    = {Mejia-Monasterio, Carlos and Metzler, Ralf and Vollmer, J{\"u}rgen},
  title     = {Editorial: anomalous transport},
  series = {Frontiers in Physics},
  volume    = {8},
  journal   = {Frontiers in Physics},
  publisher = {Frontiers Media},
  address   = {Lausanne},
  issn      = {2296-424X},
  doi       = {10.3389/fphy.2020.622417},
  pages     = {4},
  year      = {2020},
  language  = {en}
}
@misc{VarykhalovFreyseAguileraetal.2020,
  author    = {Varykhalov, Andrei and Freyse, Friedrich and Aguilera, Irene and Battiato, Marco and Krivenkov, Maxim and Marchenko, Dmitry and Bihlmayer, Gustav and Blugel, Stefan and Rader, Oliver and Sanchez-Barriga, Jaime},
  title     = {Effective mass enhancement and ultrafast electron dynamics of Au(111) surface state coupled to a quantum well},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-54989},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-549892},
  pages     = {11},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{VarykhalovFreyseAguileraetal.2020,
  author    = {Varykhalov, Andrei and Freyse, Friedrich and Aguilera, Irene and Battiato, Marco and Krivenkov, Maxim and Marchenko, Dmitry and Bihlmayer, Gustav and Blugel, Stefan and Rader, Oliver and Sanchez-Barriga, Jaime},
  title     = {Effective mass enhancement and ultrafast electron dynamics of Au(111) surface state coupled to a quantum well},
  series = {Physical Review Research},
  volume    = {2},
  journal   = {Physical Review Research},
  number    = {1},
  publisher = {American Physical Society},
  address   = {Ridge, NY},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevResearch.2.013343},
  pages     = {1 -- 9},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@phdthesis{Knigge2020,
  author    = {Knigge, Xenia},
  title     = {Einzelmolek{\"u}l-Manipulation mittels Nano-Elektroden und Dielektrophorese},
  doi       = {10.25932/publishup-44313},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-443137},
  school      = {Universit{\"a}t Potsdam},
  pages     = {106, xxxii},
  year      = {2020},
  abstract  = {In dieser Arbeit wurden Nano-Elektroden-Arrays zur Einzel-Objekt-Immobilisierung mittels Dielektrophorese verwendet. Hierbei wurden fluoreszenzmarkierte Nano-Sph{\"a}ren als Modellsystem untersucht und die gewonnenen Ergebnisse auf biologische Proben {\"u}bertragen. Die Untersuchungen in Kombination mit verschiedenen Elektrodenlayouts f{\"u}hrten zu einer deterministischen Vereinzelung der Nano-Sph{\"a}ren ab einem festen Gr{\"o}ßenverh{\"a}ltnis zwischen Nano-Sph{\"a}re und Durchmesser der Elektrodenspitzen. An den Proteinen BSA und R-PE konnte eine dielektrophoretische Immobilisierung ebenfalls demonstriert und R-PE Molek{\"u}le zur Vereinzelung gebracht werden. Hierf{\"u}r war neben einem optimierten Elektrodenlayout, das durch Feldsimulationen den Feldgradienten betreffend gesucht wurde, eine Optimierung der Feldparameter, insbesondere von Spannung und Frequenz, erforderlich. Neben der Dielektrophorese erfolgten auch Beobachtungen anderer Effekte des elektrischen Feldes, wie z.B. Elektrolyse an Nano-Elektroden und Str{\"o}mungen {\"u}ber dem Elektroden-Array, hervorgerufen durch Joulesche W{\"a}rme und AC-elektroosmotischen Fluss. Zudem konnte Dielektrophorese an Silberpartikeln beobachtet werden und mittels Fluoreszenz-, Atom-Kraft-, Raster-Elektronen-Mikroskopie und energiedispersiver R{\"o}ntgenspektroskopie untersucht werden. Schließlich wurden die verwendeten Objektive und Kameras auf ihre Lichtempfindlichkeit hin analysiert, so dass die Vereinzelung von Biomolek{\"u}len an Nano-Elektroden nachweisbar war. Festzuhalten bleibt also, dass die Vereinzelung von Nano-Objekten und Biomolek{\"u}len an Nano-Elektroden-Arrays gelungen ist. Durch den parallelen Ansatz erlaubt dies, Aussagen {\"u}ber das Verhalten von Einzelmolek{\"u}len mit guter Statistik zu treffen.},
  language  = {de}
}
@phdthesis{Wang2020,
  author    = {Wang, Jingwen},
  title     = {Electret properties of polypropylene with surface chemical modification and crystalline reconstruction},
  doi       = {10.25932/publishup-47027},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-470271},
  school      = {Universit{\"a}t Potsdam},
  pages     = {vi, 121},
  year      = {2020},
  abstract  = {As one of the most-produced commodity polymers, polypropylene draws considerable scientific and commercial interest as an electret material. In the present thesis, the influence of the surface chemical modification and crystalline reconstruction on the electret properties of the polypropylene thin films will be discussed. The chemical treatment with orthophosphoric acid can significantly improve the surface charge stability of the polypropylene electrets by introducing phosphorus- and oxygen-containing structures onto the modified surface. The thermally stimulated discharge measurement and charge profiling by means of piezoelectrically generated pressure steps are used to investigate the electret behaviour. It is concluded that deep traps of limited number density are created during the treatment with inorganic chemicals. Hence, the improvement dramatically decreases when the surface-charge density is substantially higher than ±1.2×10^(-3) C·m^(-2). The newly formed traps also show a higher trapping energy for negative charges. The energetic distributions of the traps in the non-treated and chemically treated samples offer an insight regarding the surface and foreign-chemical dominance on the charge storage and transport in the polypropylene electrets. Additionally, different electret properties are observed on the polypropylene films with the spherulitic and transcrystalline structures. It indicates the dependence of the charge storage and transport on the crystallite and molecular orientations in the crystalline phase. In general, a more diverse crystalline growth in the spherulitic samples can result in a more complex energetic trap distribution, in comparison to that in a transcrystalline polypropylene. The double-layer transcrystalline polypropylene film with a crystalline interface in the middle can be obtained by crystallising the film in contact with rough moulding surfaces on both sides. A layer of heterocharges appears on each side of the interface in the double-layer transcrystalline polypropylene electrets after the thermal poling. However, there is no charge captured within the transcrystalline layers. The phenomenon reveals the importance of the crystalline interface in terms of creating traps with the higher activation energy in polypropylene. The present studies highlight the fact that even slight variations in the polypropylene film may lead to dramatic differences in its electret properties.},
  language  = {en}
}
@article{RuedigerKuekerKaepylae2020,
  author    = {R{\"u}diger, G{\"u}nther and K{\"u}ker, Manfred and K{\"a}pyl{\"a}, Petri J.},
  title     = {Electrodynamics of turbulent fluids with fluctuating electric conductivity},
  series = {Journal of plasma physics},
  volume    = {86},
  journal   = {Journal of plasma physics},
  number    = {3},
  publisher = {Cambridge Univ. Press},
  address   = {London},
  issn      = {0022-3778},
  doi       = {10.1017/S0022377820000665},
  pages     = {14},
  year      = {2020},
  abstract  = {Consequences of fluctuating microscopic conductivity in mean-field electrodynamics of turbulent fluids are formulated and discussed. If the conductivity fluctuations are assumed to be uncorrelated with the velocity fluctuations then only the turbulence-originated magnetic diffusivity of the fluid is reduced and the decay time of a large-scale magnetic field or the cycle times of oscillating turbulent dynamo models are increased. If, however, the fluctuations of conductivity and flow in a certain well-defined direction are correlated, an additional diamagnetic pumping effect results, transporting the magnetic field in the opposite direction to the diffusivity flux vector <eta'u'>. In the presence of global rotation, even for homogeneous turbulence fields, an alpha effect appears. If the characteristic values of the outer core of the Earth or the solar convection zone are applied, the dynamo number of the new alpha effect does not reach supercritical values to operate as an alpha(2)-dynamo but oscillating alpha Omega-dynamos with differential rotation are not excluded.},
  language  = {en}
}
@article{SchneiderHoffmannVogel2020,
  author    = {Schneider, Sebastian and Hoffmann-Vogel, Regina},
  title     = {Electrostatic forces above graphene nanoribbons and edges interpreted as partly hydrogen-free},
  series = {Nanoscale},
  volume    = {12},
  journal   = {Nanoscale},
  number    = {34},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2040-3364},
  doi       = {10.1039/d0nr03348k},
  pages     = {17895 -- 17901},
  year      = {2020},
  abstract  = {Graphene nanoribbons' electronic transport properties strongly depend on the type of edge, armchair, zigzag or other, and on edge functionalization that can be used for band-gap engineering. For only partly hydrogenated edges interesting magnetic properties are predicted. Electric charge accumulates at edges and corners. Scanning force microscopy has so far shown the centre of graphene nanoribbons with atomic resolution using a quartz crystal tuning fork sensor of high stiffness. Weak long-range electrostatic forces related to the charge accumulation on the edges of graphene nanoribbons could not be imaged so far. Here, we show the electrostatic forces at the corners and edges of graphene nanoribbons are amenable to measurement. We use soft cantilevers and a bimodal imaging technique to combine enhanced sensitivity to weak long-range electrostatic forces with the high resolution of the second-frequency shift. Additionally, in our work the edges of the nanoribbons are mainly hydrogen-free, opening to the route to investigations of partly hydrogenated magnetic nanoribbons.},
  language  = {en}
}
@article{MohammadyAuffevesAnders2020,
  author    = {Mohammady, M. Hamed and Auff{\`e}ves, Alexia and Anders, Janet},
  title     = {Energetic footprints of irreversibility in the quantum regime},
  series = {Communications Physics},
  volume    = {3},
  journal   = {Communications Physics},
  number    = {1},
  publisher = {Springer Nature},
  address   = {London},
  issn      = {2399-3650},
  doi       = {10.1038/s42005-020-0356-9},
  pages     = {1 -- 14},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@misc{MohammadyAuffevesAnders2020,
  author    = {Mohammady, M. Hamed and Auff{\`e}ves, Alexia and Anders, Janet},
  title     = {Energetic footprints of irreversibility in the quantum regime},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51676},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-516766},
  pages     = {16},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{HolmesAndersMintert2020,
  author    = {Holmes, Zoe and Anders, Janet and Mintert, Florian},
  title     = {Enhanced energy transfer to an optomechanical piston from indistinguishable photons},
  series = {Physical review letters},
  volume    = {124},
  journal   = {Physical review letters},
  number    = {21},
  publisher = {American Physical Society},
  address   = {College Park, Md.},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.124.210601},
  pages     = {6},
  year      = {2020},
  abstract  = {Thought experiments involving gases and pistons, such as Maxwell's demon and Gibbs' mixing, are central to our understanding of thermodynamics. Here, we present a quantum thermodynamic thought experiment in which the energy transfer from two photonic gases to a piston membrane grows quadratically with the number of photons for indistinguishable gases, while it grows linearly for distinguishable gases. This signature of bosonic bunching may be observed in optomechanical experiments, highlighting the potential of these systems for the realization of thermodynamic thought experiments in the quantum realm.},
  language  = {en}
}
@article{HortonKhanCahilletal.2020,
  author    = {Horton, Benjamin P. and Khan, Nicole S. and Cahill, Niamh and Lee, Janice S. H. and Shaw, Timothy A. and Garner, Andra J. and Kemp, Andrew C. and Engelhart, Simon E. and Rahmstorf, Stefan},
  title     = {Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from an expert survey},
  series = {npj Climate and Atmospheric Science},
  volume    = {3},
  journal   = {npj Climate and Atmospheric Science},
  number    = {1},
  publisher = {Springer Nature},
  address   = {London},
  issn      = {2397-3722},
  doi       = {10.1038/s41612-020-0121-5},
  pages     = {1 -- 8},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@misc{HortonKhanCahilletal.2020,
  author    = {Horton, Benjamin P. and Khan, Nicole S. and Cahill, Niamh and Lee, Janice S. H. and Shaw, Timothy A. and Garner, Andra J. and Kemp, Andrew C. and Engelhart, Simon E. and Rahmstorf, Stefan},
  title     = {Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from an expert survey},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51678},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-516788},
  pages     = {10},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{GrebenkovSposiniMetzleretal.2020,
  author    = {Grebenkov, Denis S. and Sposini, Vittoria and Metzler, Ralf and Oshanin, Gleb and Seno, Flavio},
  title     = {Exact distributions of the maximum and range of random diffusivity processes},
  series = {New Journal of Physics},
  volume    = {23},
  journal   = {New Journal of Physics},
  publisher = {Dt. Physikalische Ges.},
  address   = {Bad Honnef},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/abd313},
  pages     = {23},
  year      = {2020},
  abstract  = {We study the extremal properties of a stochastic process xt defined by the Langevin equation ẋₜ =√2Dₜ ξₜ, in which ξt is a Gaussian white noise with zero mean and Dₜ is a stochastic'diffusivity', defined as a functional of independent Brownian motion Bₜ.We focus on threechoices for the random diffusivity Dₜ: cut-off Brownian motion, Dₜt ∼ Θ(Bₜ), where Θ(x) is the Heaviside step function; geometric Brownian motion, Dₜ ∼ exp(-Bₜ); and a superdiffusive process based on squared Brownian motion, Dₜ ∼ B²ₜ. For these cases we derive exact expressions for the probability density functions of the maximal positive displacement and of the range of the process xₜ on the time interval ₜ ∈ (0, T).We discuss the asymptotic behaviours of the associated probability density functions, compare these against the behaviour of the corresponding properties of standard Brownian motion with constant diffusivity (Dₜ = D0) and also analyse the typical behaviour of the probability density functions which is observed for a majority of realisations of the stochastic diffusivity process.},
  language  = {en}
}
@misc{GrebenkovSposiniMetzleretal.2020,
  author    = {Grebenkov, Denis S. and Sposini, Vittoria and Metzler, Ralf and Oshanin, Gleb and Seno, Flavio},
  title     = {Exact distributions of the maximum and range of random diffusivity processes},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1142},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-50397},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-503976},
  pages     = {24},
  year      = {2020},
  abstract  = {We study the extremal properties of a stochastic process xt defined by the Langevin equation ẋₜ =√2Dₜ ξₜ, in which ξt is a Gaussian white noise with zero mean and Dₜ is a stochastic'diffusivity', defined as a functional of independent Brownian motion Bₜ.We focus on threechoices for the random diffusivity Dₜ: cut-off Brownian motion, Dₜt ∼ Θ(Bₜ), where Θ(x) is the Heaviside step function; geometric Brownian motion, Dₜ ∼ exp(-Bₜ); and a superdiffusive process based on squared Brownian motion, Dₜ ∼ B²ₜ. For these cases we derive exact expressions for the probability density functions of the maximal positive displacement and of the range of the process xₜ on the time interval ₜ ∈ (0, T).We discuss the asymptotic behaviours of the associated probability density functions, compare these against the behaviour of the corresponding properties of standard Brownian motion with constant diffusivity (Dₜ = D0) and also analyse the typical behaviour of the probability density functions which is observed for a majority of realisations of the stochastic diffusivity process.},
  language  = {en}
}
@article{YochelisBetaGov2020,
  author    = {Yochelis, Arik and Beta, Carsten and Gov, Nir S.},
  title     = {Excitable solitons},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {101},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  number    = {2},
  publisher = {American Physical Society},
  address   = {Melville, NY},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.101.022213},
  pages     = {6},
  year      = {2020},
  abstract  = {Excitable pulses are among the most widespread dynamical patterns that occur in many different systems, ranging from biological cells to chemical reactions and ecological populations. Traditionally, the mutual annihilation of two colliding pulses is regarded as their prototypical signature. Here we show that colliding excitable pulses may exhibit solitonlike crossover and pulse nucleation if the system obeys a mass conservation constraint. In contrast to previous observations in systems without mass conservation, these alternative collision scenarios are robustly observed over a wide range of parameters. We demonstrate our findings using a model of intracellular actin waves since, on time scales of wave propagations over the cell scale, cells obey conservation of actin monomers. The results provide a key concept to understand the ubiquitous occurrence of actin waves in cells, suggesting why they are so common, and why their dynamics is robust and long-lived.},
  language  = {en}
}
@article{TokmoldinHosseiniRaoufietal.2020,
  author    = {Tokmoldin, Nurlan and Hosseini, Seyed Mehrdad and Raoufi, Meysam and Phuong, Le Quang and Sandberg, Oskar J. and Guan, Huilan and Zou, Yingping and Neher, Dieter and Shoaee, Safa},
  title     = {Extraordinarily long diffusion length in PM6:Y6 organic solar cells},
  series = {Journal of materials chemistry : A, materials for energy and sustainability},
  volume    = {8},
  journal   = {Journal of materials chemistry : A, materials for energy and sustainability},
  number    = {16},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2050-7488},
  doi       = {10.1039/d0ta03016c},
  pages     = {7854 -- 7860},
  year      = {2020},
  abstract  = {The PM6:Y6 bulk-heterojunction (BHJ) blend system achieves high short-circuit current (J(SC)) values in thick photovoltaic junctions. Here we analyse these solar cells to understand the observed independence of the short-circuit current upon photoactive layer thickness. We employ a range of optoelectronic measurements and analyses, including Mott-Schottky analysis, CELIV, photoinduced absorption spectroscopy, mobility measurements and simulations, to conclude that, the invariant photocurrent for the devices with different active layer thicknesses is associated with the Y6's diffusion length exceeding 300 nm in case of a 300 nm thick cell. This is despite unintentional doping that occurs in PM6 and the associated space-charge effect, which is expected to be even more profound upon photogeneration. This extraordinarily long diffusion length - which is an order of magnitude larger than typical values for organics - dominates transport in the flat-band region of thick junctions. Our work suggests that the performance of the doped PM6:Y6 organic solar cells resembles that of inorganic devices with diffusion transport playing a pivotal role. Ultimately, this is expected to be a key requirement for the fabrication of efficient, high-photocurrent, thick organic solar cells.},
  language  = {en}
}
@article{GarciaBenitoQuartiQuelozetal.2020,
  author    = {Garc{\´i}a-Benito, In{\´e}s and Quarti, Claudio and Queloz, Valentin I. E. and Hofstetter, Yvonne J. and Becker-Koch, David and Caprioglio, Pietro and Neher, Dieter and Orlandi, Simonetta and Cavazzini, Marco and Pozzi, Gianluca and Even, Jacky and Nazeeruddin, Mohammad Khaja and Vaynzof, Yana and Grancini, Giulia},
  title     = {Fluorination of organic spacer impacts on the structural and optical response of 2D perovskites},
  series = {Frontiers in Chemistry},
  volume    = {7},
  journal   = {Frontiers in Chemistry},
  publisher = {Frontiers Media},
  address   = {Lausanne},
  issn      = {2296-2646},
  doi       = {10.3389/fchem.2019.00946},
  pages     = {1 -- 11},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@misc{GarciaBenitoQuartiQuelozetal.2020,
  author    = {Garc{\´i}a-Benito, In{\´e}s and Quarti, Claudio and Queloz, Valentin I. E. and Hofstetter, Yvonne J. and Becker-Koch, David and Caprioglio, Pietro and Neher, Dieter and Orlandi, Simonetta and Cavazzini, Marco and Pozzi, Gianluca and Even, Jacky and Nazeeruddin, Mohammad Khaja and Vaynzof, Yana and Grancini, Giulia},
  title     = {Fluorination of organic spacer impacts on the structural and optical response of 2D perovskites},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51242},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-512420},
  pages     = {13},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{JelkenHenkelSanter2020,
  author    = {Jelken, Joachim and Henkel, Carsten and Santer, Svetlana},
  title     = {Formation of half-period surface relief gratings in azobenzene containing polymer films},
  series = {Applied physics : B, Lasers and optics},
  volume    = {126},
  journal   = {Applied physics : B, Lasers and optics},
  number    = {9},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-020-07500-w},
  pages     = {14},
  year      = {2020},
  abstract  = {We study the peculiar response of photo-sensitive polymer films irradiated with a certain type of interference pattern where one interfering beam is S-polarized, while the second one is P-polarized. The polymer film, although in a glassy state, deforms following the local polarization distribution of the incident light, and a surface relief grating (SRG) appears whose period is half the optical one. All other types of interference patterns result in the matching of both periods. The topographical response is triggered by the alignment of photo-responsive azobenzene containing polymer side chains orthogonal to the local electrical field, resulting in a bulk birefringence grating (BBG). We investigate the process of dual grating formation (SRG and BBG) in a polymer film utilizing a dedicated set-up that combines probe beam diffraction and atomic force microscopy (AFM) measurements, and permits acquiring in situ and in real-time information about changes in local topography and birefringence. We find that the SRG maxima appear at the positions of linearly polarized light (tilted by 45 degrees relative to the grating vector), causing the formation of the half-period topography. This permits to inscribe symmetric and asymmetric topography gratings with sub-wavelength period, while changing only slightly the polarization of one of the interfering beams. We demonstrate an easy generation of sawtooth profiles (blazed gratings) with adjustable shape. With these results, we have taken a significant step in understanding the photo-induced deformation of azo-polymer films.},
  language  = {en}
}
@article{FernandezBrunoGarcesetal.2020,
  author    = {Fernandez, Ricardo and Bruno, Giovanni and Garces, Gerardo and Nieto-Luis, H. and Gonzalez-Doncel, Gaspar},
  title     = {Fractional brownian motion of dislocations during creep deformation of metals},
  series = {Materials science \& engineering. A, Structural materials},
  volume    = {796},
  journal   = {Materials science \& engineering. A, Structural materials},
  publisher = {Elsevier},
  address   = {Lausanne},
  issn      = {0921-5093},
  doi       = {10.1016/j.msea.2020.140013},
  pages     = {8},
  year      = {2020},
  abstract  = {The present work offers an explanation on how the long-range interaction of dislocations influences their movement, and therefore the strain, during creep of metals. It is proposed that collective motion of dislocations can be described as a fractional Brownian motion. This explains the noisy appearance of the creep strain signal as a function of time. Such signal is split into a deterministic and a stochastic part. These terms can be related to two kinds of dislocation motions: individual and collective, respectively. The description is consistent with the fractal nature of strain-induced dislocation structures predicated in previous works. Moreover, it encompasses the evolution of the strain rate during all stages of creep, including the tertiary one. Creep data from Al99.8\% and Al3.85\%Mg tested at different temperatures and stresses are used to validate the proposed ideas: it is found that different creep stages present different diffusion characters, and therefore different dislocation motion character.},
  language  = {en}
}
@article{WangCherstvyChechkinetal.2020,
  author    = {Wang, Wei and Cherstvy, Andrey G. and Chechkin, Aleksei V. and Thapa, Samudrajit and Seno, Flavio and Liu, Xianbin and Metzler, Ralf},
  title     = {Fractional Brownian motion with random diffusivity},
  series = {Journal of physics : A, Mathematical and theoretical},
  volume    = {53},
  journal   = {Journal of physics : A, Mathematical and theoretical},
  number    = {47},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1751-8113},
  doi       = {10.1088/1751-8121/aba467},
  pages     = {34},
  year      = {2020},
  abstract  = {Numerous examples for a priori unexpected non-Gaussian behaviour for normal and anomalous diffusion have recently been reported in single-particle tracking experiments. Here, we address the case of non-Gaussian anomalous diffusion in terms of a random-diffusivity mechanism in the presence of power-law correlated fractional Gaussian noise. We study the ergodic properties of this model via examining the ensemble- and time-averaged mean-squared displacements as well as the ergodicity breaking parameter EB quantifying the trajectory-to-trajectory fluctuations of the latter. For long measurement times, interesting crossover behaviour is found as function of the correlation time tau characterising the diffusivity dynamics. We unveil that at short lag times the EB parameter reaches a universal plateau. The corresponding residual value of EB is shown to depend only on tau and the trajectory length. The EB parameter at long lag times, however, follows the same power-law scaling as for fractional Brownian motion. We also determine a corresponding plateau at short lag times for the discrete representation of fractional Brownian motion, absent in the continuous-time formulation. These analytical predictions are in excellent agreement with results of computer simulations of the underlying stochastic processes. Our findings can help distinguishing and categorising certain nonergodic and non-Gaussian features of particle displacements, as observed in recent single-particle tracking experiments.},
  language  = {en}
}
@phdthesis{Brose2020,
  author    = {Brose, Robert},
  title     = {From dawn till dusk},
  doi       = {10.25932/publishup-47086},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-470865},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xiii, 146},
  year      = {2020},
  abstract  = {Supernova remnants are believed to be the source of cosmic rays with energies up to 10^15 eV that are produced within our Galaxy. The acceleration mechanism associated with the collision-less shocks in supernova remnants - diffusive shock acceleration - predicts a spectral index of the accelerated non-thermal particles of s = 2. However, measurements of non-thermal emission in radio, X-rays and gamma-rays reveal significant deviations of the particles spectral index from the canonical value of s = 2. The youngest Galactic supernova remnant G1.9+0.3 is an interesting target for next-generation gamma-ray observatories. So far, the remnant is only detected in the radio and the X-ray bands, but its young age of ≈100 yrs and inferred shock speed of ≈ 14, 000 km/s could make it an efficient particle accelerator. I performed spherical symmetric 1D simulations with the RATPaC code, in which I simultaneously solved the transport equation for cosmic rays, the transport equation for magnetic turbulence, and the hydro-dynamical equations for the gas flow. Separately computed distributions of the particles accelerated at the forward and the reverse shock were then used to calculate the spectra of synchrotron, inverse Compton, and Pion-decay radiation from the source. The emission from G1.9+0.3 can be self-consistently explained within the test-particle limit. I find that the X-ray flux is dominated by emission from the forward shock while most of the radio emission originates near the reverse shock, which makes G1.9+0.3 the first remnant with non-thermal radiation detected from the reverse shock. The flux of very-high-energy gamma-ray emission from G1.9+0.3 is expected to be close to the sensitivity threshold of the Cherenkov Telescope Array. The limited time available to grow large-scale turbulence limits the maximum energy of particles to values below 100 TeV, hence G1.9+0.3 is not a PeVatron. Although there are many models for the acceleration of cosmic rays in Supernova remnants, the escape of cosmic rays from these sources is yet understudied. I use our time-dependent acceleration code RATPaC to study the acceleration of cosmic rays and their escape in post-adiabatic Supernova remnants and calculate the subsequent gamma-ray emission from inverse-Compton scattering and Pion decay. My simulations span 100,000 years, thus covering the free-expansion, the Sedov-Taylor, and the beginning of the post-adiabatic phase of the remnant's evolution. At later stages of the evolution cosmic rays over a wide range of energy can reside outside of the remnant, creating spectra that are softer than predicted by standard diffusive shock acceleration and feature breaks in the 10 - 100 GeV-range. The total spectrum of cosmic rays released into the interstellar medium has a spectral index of s ≈ 2.4 above roughly 10 GeV which is close to that required by Galactic propagation models. I further find the gamma-ray luminosity to peak around an age of 4,000 years for inverse-Compton-dominated high-energy emission. Remnants expanding in low-density media emit generally more inverse-Compton radiation matching the fact that the brightest known supernova remnants - RCW86, Vela Jr, HESSJ1721-347 and RXJ1713.7-3946 - are all expanding in low density environments. The importance of feedback from the cosmic-rays on the hydrodynamical evolution of the remnants is debated as a possibility to obtain soft cosmic-ray spectra at low energies. I performed spherically symmetric 1-D simulations with a modified version of the RATPaC code, in which I simultaneously solve the transport equation for cosmic rays and the hydrodynamical equations, including the back-reaction of the cosmic-ray pressure on the flow profiles. Besides the known modification of the flow profiles and the consequently curved cosmic-ray spectra, steady-state models for non-linear diffusive shock acceleration overpredict the total compression ratio that can be reached with cosmic-ray feedback, as there is limited time for building these modifications. Further, I find modifications to the downstream flow structure that change the evolutionary behavior of the remnant and trigger a cosmic-ray-induced instability close to the contact discontinuity, if and when the cosmic-ray pressure becomes dominant there.},
  language  = {en}
}
@misc{GrebenkovMetzlerOshanin2020,
  author    = {Grebenkov, Denis S. and Metzler, Ralf and Oshanin, Gleb},
  title     = {From single-particle stochastic kinetics to macroscopic reaction rates},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1018},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-48405},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-484059},
  pages     = {29},
  year      = {2020},
  abstract  = {We consider the first-passage problem for N identical independent particles that are initially released uniformly in a finite domain Ω and then diffuse toward a reactive area Γ, which can be part of the outer boundary of Ω or a reaction centre in the interior of Ω. For both cases of perfect and partial reactions, we obtain the explicit formulas for the first two moments of the fastest first-passage time (fFPT), i.e., the time when the first out of the N particles reacts with Γ. Moreover, we investigate the full probability density of the fFPT. We discuss a significant role of the initial condition in the scaling of the average fFPT with the particle number N, namely, a much stronger dependence (1/N and 1/N² for partially and perfectly reactive targets, respectively), in contrast to the well known inverse-logarithmic behaviour found when all particles are released from the same fixed point. We combine analytic solutions with scaling arguments and stochastic simulations to rationalise our results, which open new perspectives for studying the relevance of multiple searchers in various situations of molecular reactions, in particular, in living cells.},
  language  = {en}
}
@article{GrebenkovMetzlerOshanin2020,
  author    = {Grebenkov, Denis S. and Metzler, Ralf and Oshanin, Gleb},
  title     = {From single-particle stochastic kinetics to macroscopic reaction rates},
  series = {New Journal of Physics},
  volume    = {22},
  journal   = {New Journal of Physics},
  publisher = {Dt. Physikalische Ges.},
  address   = {Bad Honnef},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/abb1de},
  pages     = {28},
  year      = {2020},
  abstract  = {We consider the first-passage problem for N identical independent particles that are initially released uniformly in a finite domain Ω and then diffuse toward a reactive area Γ, which can be part of the outer boundary of Ω or a reaction centre in the interior of Ω. For both cases of perfect and partial reactions, we obtain the explicit formulas for the first two moments of the fastest first-passage time (fFPT), i.e., the time when the first out of the N particles reacts with Γ. Moreover, we investigate the full probability density of the fFPT. We discuss a significant role of the initial condition in the scaling of the average fFPT with the particle number N, namely, a much stronger dependence (1/N and 1/N² for partially and perfectly reactive targets, respectively), in contrast to the well known inverse-logarithmic behaviour found when all particles are released from the same fixed point. We combine analytic solutions with scaling arguments and stochastic simulations to rationalise our results, which open new perspectives for studying the relevance of multiple searchers in various situations of molecular reactions, in particular, in living cells.},
  language  = {en}
}
@article{StojkoskiSandevBasnarkovetal.2020,
  author    = {Stojkoski, Viktor and Sandev, Trifce and Basnarkov, Lasko and Kocarev, Ljupco and Metzler, Ralf},
  title     = {Generalised geometric Brownian motion},
  series = {Entropy},
  volume    = {22},
  journal   = {Entropy},
  number    = {12},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {1099-4300},
  doi       = {10.3390/e22121432},
  pages     = {34},
  year      = {2020},
  abstract  = {Classical option pricing schemes assume that the value of a financial asset follows a geometric Brownian motion (GBM). However, a growing body of studies suggest that a simple GBM trajectory is not an adequate representation for asset dynamics, due to irregularities found when comparing its properties with empirical distributions. As a solution, we investigate a generalisation of GBM where the introduction of a memory kernel critically determines the behaviour of the stochastic process. We find the general expressions for the moments, log-moments, and the expectation of the periodic log returns, and then obtain the corresponding probability density functions using the subordination approach. Particularly, we consider subdiffusive GBM (sGBM), tempered sGBM, a mix of GBM and sGBM, and a mix of sGBMs. We utilise the resulting generalised GBM (gGBM) in order to examine the empirical performance of a selected group of kernels in the pricing of European call options. Our results indicate that the performance of a kernel ultimately depends on the maturity of the option and its moneyness.},
  language  = {en}
}
@article{AlbrechtWinkelmannLevermann2020,
  author    = {Albrecht, Torsten and Winkelmann, Ricarda and Levermann, Anders},
  title     = {Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)},
  series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
  volume    = {14},
  journal   = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
  number    = {2},
  publisher = {Copernicus Publ.},
  address   = {G{\"o}ttingen},
  issn      = {1994-0416},
  doi       = {10.5194/tc-14-633-2020},
  pages     = {633 -- 656},
  year      = {2020},
  abstract  = {The Parallel Ice Sheet Model (PISM) is applied to the Antarctic Ice Sheet over the last two glacial cycles (approximate to 210 000 years) with a resolution of 16 km. An ensemble of 256 model runs is analyzed in which four relevant model parameters have been systematically varied using full-factorial parameter sampling. Parameters and plausible parameter ranges have been identified in a companion paper (Albrecht et al., 2020) and are associated with ice dynamics, climatic forcing, basal sliding and bed deformation and represent distinct classes of model uncertainties. The model is scored against both modern and geologic data, including reconstructed grounding-line locations, elevation-age data, ice thickness, surface velocities and uplift rates. An aggregated score is computed for each ensemble member that measures the overall model-data misfit, including measurement uncertainty in terms of a Gaussian error model (Briggs and Tarasov, 2013). The statistical method used to analyze the ensemble simulation results follows closely the simple averaging method described in Pollard et al. (2016). This analysis reveals clusters of best-fit parameter combinations, and hence a likely range of relevant model and boundary parameters, rather than individual best-fit parameters. The ensemble of reconstructed histories of Antarctic Ice Sheet volumes provides a score-weighted likely range of sea-level contributions since the Last Glacial Maximum (LGM) of 9.4 +/- 4.1m (or 6.5 +/- 2.0 x 10(6) km(3)), which is at the upper range of most previous studies. The last deglaciation occurs in all ensemble simulations after around 12 000 years before present and hence after the meltwater pulse 1A (MWP1a). Our ensemble analysis also provides an estimate of parametric uncertainty bounds for the present-day state that can be used for PISM projections of future sea-level contributions from the Antarctic Ice Sheet.},
  language  = {en}
}
@article{WunderlingWilleitDongesetal.2020,
  author    = {Wunderling, Nico and Willeit, Matteo and Donges, Jonathan and Winkelmann, Ricarda},
  title     = {Global warming due to loss of large ice masses and Arctic summer sea ice},
  series = {Nature Communications},
  volume    = {11},
  journal   = {Nature Communications},
  number    = {1},
  publisher = {Nature Publishing Group},
  address   = {Berlin},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-020-18934-3},
  pages     = {14},
  year      = {2020},
  abstract  = {Several large-scale cryosphere elements such as the Arctic summer sea ice, the mountain glaciers, the Greenland and West Antarctic Ice Sheet have changed substantially during the last century due to anthropogenic global warming. However, the impacts of their possible future disintegration on global mean temperature (GMT) and climate feedbacks have not yet been comprehensively evaluated. Here, we quantify this response using an Earth system model of intermediate complexity. Overall, we find a median additional global warming of 0.43 degrees C (interquartile range: 0.39-0.46 degrees C) at a CO2 concentration of 400 ppm. Most of this response (55\%) is caused by albedo changes, but lapse rate together with water vapour (30\%) and cloud feedbacks (15\%) also contribute significantly. While a decay of the ice sheets would occur on centennial to millennial time scales, the Arctic might become ice-free during summer within the 21st century. Our findings imply an additional increase of the GMT on intermediate to long time scales. The disintegration of cryosphere elements such as the Arctic summer sea ice, mountain glaciers, Greenland and West Antarctica is associated with temperature and radiative feedbacks. In this work, the authors quantify these feedbacks and find an additional global warming of 0.43 degrees C.},
  language  = {en}
}
@article{MkrtchianHenkel2020,
  author    = {Mkrtchian, Vanik E. and Henkel, Carsten},
  title     = {Green function solution of generalised boundary value problems},
  series = {Physics Letters A},
  volume    = {384},
  journal   = {Physics Letters A},
  number    = {23},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0375-9601},
  doi       = {10.1016/j.physleta.2020.126573},
  pages     = {5},
  year      = {2020},
  abstract  = {We construct an expression for the Green function of a differential operator satisfying nonlocal, homogeneous boundary conditions starting from the fundamental solution of the differential operator. This also provides the solution to the boundary value problem of an inhomogeneous partial differential equation with inhomogeneous, nonlocal boundary conditions. The construction applies for a broad class of linear partial differential equations and linear boundary conditions.},
  language  = {en}
}
@article{XuLiuLietal.2020,
  author    = {Xu, Yong and Liu, Xuemei and Li, Yongge and Metzler, Ralf},
  title     = {Heterogeneous diffusion processes and nonergodicity with Gaussian colored noise in layered diffusivity landscapes},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {102},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  number    = {6},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.102.062106},
  pages     = {16},
  year      = {2020},
  abstract  = {Heterogeneous diffusion processes (HDPs) with space-dependent diffusion coefficients D(x) are found in a number of real-world systems, such as for diffusion of macromolecules or submicron tracers in biological cells. Here, we examine HDPs in quenched-disorder systems with Gaussian colored noise (GCN) characterized by a diffusion coefficient with a power-law dependence on the particle position and with a spatially random scaling exponent. Typically, D(x) is considered to be centerd at the origin and the entire x axis is characterized by a single scaling exponent a. In this work we consider a spatially random scenario: in periodic intervals ("layers") in space D(x) is centerd to the midpoint of each interval. In each interval the scaling exponent alpha is randomly chosen from a Gaussian distribution. The effects of the variation of the scaling exponents, the periodicity of the domains ("layer thickness") of the diffusion coefficient in this stratified system, and the correlation time of the GCN are analyzed numerically in detail. We discuss the regimes of superdiffusion, subdiffusion, and normal diffusion realisable in this system. We observe and quantify the domains where nonergodic and non-Gaussian behaviors emerge in this system. Our results provide new insights into the understanding of weak ergodicity breaking for HDPs driven by colored noise, with potential applications in quenched layered systems, typical model systems for diffusion in biological cells and tissues, as well as for diffusion in geophysical systems.},
  language  = {en}
}
@article{SandevIominKocarev2020,
  author    = {Sandev, Trifce and Iomin, Alexander and Kocarev, Ljupco},
  title     = {Hitting times in turbulent diffusion due to multiplicative noise},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {102},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Woodbury, NY},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.102.042109},
  pages     = {10},
  year      = {2020},
  abstract  = {We study a distribution of times of the first arrivals to absorbing targets in turbulent diffusion, which is due to a multiplicative noise. Two examples of dynamical systems with a multiplicative noise are studied. The first one is a random process according to inhomogeneous diffusion, which is also known as a geometric Brownian motion in the Black-Scholes model. The second model is due to a random processes on a two-dimensional comb, where inhomogeneous advection is possible only along the backbone, while Brownian diffusion takes place inside the branches. It is shown that in both cases turbulent diffusion takes place as the one-dimensional random process with the log-normal distribution in the presence of absorbing targets, which are characterized by the Levy-Smirnov distribution for the first hitting times.},
  language  = {en}
}
@article{JiangTaoStolterfohtetal.2020,
  author    = {Jiang, Wei and Tao, Chen and Stolterfoht, Martin and Jin, Hui and Stephen, Meera and Lin, Qianqian and Nagiri, Ravi C. R. and Burn, Paul L. and Gentle, Ian R.},
  title     = {Hole-transporting materials for low donor content organic solar cells},
  series = {Organic electronics : physics, materials and applications},
  volume    = {76},
  journal   = {Organic electronics : physics, materials and applications},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1566-1199},
  doi       = {10.1016/j.orgel.2019.105480},
  pages     = {7},
  year      = {2020},
  abstract  = {Low donor content solar cells are an intriguing class of photovoltaic device about which there is still considerable discussion with respect to their mode of operation. We have synthesized a series of triphenylamine-based materials for use in low donor content devices with the electron accepting [6,6]-phenyl-C71-butyric acid methyl ester (PC(7)0BM). The triphenylamine-based materials absorb light in the near UV enabling the PC(7)0BM to be be the main light absorbing organic semiconducting material in the solar cell. It was found that the devices did not operate as classical Schottky junctions but rather photocurrent was generated by hole transfer from the photo-excited PC(7)0BM to the triphenylamine-based donors. We found that replacing the methoxy surface groups with methyl groups on the donor material led to a decrease in hole mobility for the neat films, which was due to the methyl substituted materials having the propensity to aggregate. The thermodynamic drive to aggregate was advantageous for the performance of the low donor content (6 wt\%) films. It was found that the 6 wt\% donor devices generally gave higher performance than devices containing 50 wt\% of the donor.},
  language  = {en}
}
@phdthesis{Wolff2020,
  author    = {Wolff, Christian Michael},
  title     = {Identification and reduction of losses in perovskite solar cells},
  doi       = {10.25932/publishup-47930},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-479301},
  school      = {Universit{\"a}t Potsdam},
  pages     = {x, 158},
  year      = {2020},
  abstract  = {Perovskite solar cells have become one of the most studied systems in the quest for new, cheap and efficient solar cell materials. Within a decade device efficiencies have risen to >25\% in single-junction and >29\% in tandem devices on top of silicon. This rapid improvement was in many ways fortunate, as e. g. the energy levels of commonly used halide perovskites are compatible with already existing materials from other photovoltaic technologies such as dye-sensitized or organic solar cells. Despite this rapid success, fundamental working principles must be understood to allow concerted further improvements. This thesis focuses on a comprehensive understanding of recombination processes in functioning devices. First the impact the energy level alignment between the perovskite and the electron transport layer based on fullerenes is investigated. This controversial topic is comprehensively addressed and recombination is mitigated through reducing the energy difference between the perovskite conduction band minimum and the LUMO of the fullerene. Additionally, an insulating blocking layer is introduced, which is even more effective in reducing this recombination, without compromising carrier collection and thus efficiency. With the rapid efficiency development (certified efficiencies have broken through the 20\% ceiling) and thousands of researchers working on perovskite-based optoelectronic devices, reliable protocols on how to reach these efficiencies are lacking. Having established robust methods for >20\% devices, while keeping track of possible pitfalls, a detailed description of the fabrication of perovskite solar cells at the highest efficiency level (>20\%) is provided. The fabrication of low-temperature p-i-n structured devices is described, commenting on important factors such as practical experience, processing atmosphere \& temperature, material purity and solution age. Analogous to reliable fabrication methods, a method to identify recombination losses is needed to further improve efficiencies. Thus, absolute photoluminescence is identified as a direct way to quantify the Quasi-Fermi level splitting of the perovskite absorber (1.21eV) and interfacial recombination losses the transport layers impose, reducing the latter to ~1.1eV. Implementing very thin interlayers at both the p- and n-interface (PFN-P2 and LiF, respectively), these losses are suppressed, enabling a VOC of up to 1.17eV. Optimizing the device dimensions and the bandgap, 20\% devices with 1cm2 active area are demonstrated. Another important consideration is the solar cells' stability if subjected to field-relevant stressors during operation. In particular these are heat, light, bias or a combination thereof. Perovskite layers - especially those incorporating organic cations - have been shown to degrade if subjected to these stressors. Keeping in mind that several interlayers have been successfully used to mitigate recombination losses, a family of perfluorinated self-assembled monolayers (X-PFCn, where X denotes I/Br and n = 7-12) are introduced as interlayers at the n-interface. Indeed, they reduce interfacial recombination losses enabling device efficiencies up to 21.3\%. Even more importantly they improve the stability of the devices. The solar cells with IPFC10 are stable over 3000h stored in the ambient and withstand a harsh 250h of MPP at 85◦C without appreciable efficiency losses. To advance further and improve device efficiencies, a sound understanding of the photophysics of a device is imperative. Many experimental observations in recent years have however drawn an inconclusive picture, often suffering from technical of physical impediments, disguising e. g. capacitive discharge as recombination dynamics. To circumvent these obstacles, fully operational, highly efficient perovskites solar cells are investigated by a combination of multiple optical and optoelectronic probes, allowing to draw a conclusive picture of the recombination dynamics in operation. Supported by drift-diffusion simulations, the device recombination dynamics can be fully described by a combination of first-, second- and third-order recombination and JV curves as well as luminescence efficiencies over multiple illumination intensities are well described within the model. On this basis steady state carrier densities, effective recombination constants, densities-of-states and effective masses are calculated, putting the devices at the brink of the radiative regime. Moreover, a comprehensive review of recombination in state-of-the-art devices is given, highlighting the importance of interfaces in nonradiative recombination. Different strategies to assess these are discussed, before emphasizing successful strategies to reduce interfacial recombination and pointing towards the necessary steps to further improve device efficiency and stability. Overall, the main findings represent an advancement in understanding loss mechanisms in highly efficient solar cells. Different reliable optoelectronic techniques are used and interfacial losses are found to be of grave importance for both efficiency and stability. Addressing the interfaces, several interlayers are introduced, which mitigate recombination losses and degradation.},
  language  = {en}
}
@article{Sangian2020,
  author    = {Sangian, Danial},
  title     = {Improving the performance of dielectric-elastomer actuators at elevated operating temperatures by means of thermal softening},
  series = {Smart materials and structures},
  volume    = {29},
  journal   = {Smart materials and structures},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0964-1726},
  doi       = {10.1088/1361-665X/ab6079},
  pages     = {9},
  year      = {2020},
  abstract  = {Dielectric elastomer devices operate on the principle of Maxwell stress and their operating performance significantly rely on the elastomer and compliant electrode's electrical and mechanical properties. This paper reports that performing actuation tests at elevated temperatures resulted in an enhanced performance due to the reduction of Young's modulus and the increase of dielectric permittivity. As a result, considerably higher isometric forces and isotonic strains were achieved above the ambient operating temperature. For actuators made of silicone, polyurethane and acrylic elastomers, 166\%, 70\% and 266\% higher isometric forces and 450\%, 250\% and 54\% higher isotonic strains were observed, respectively, when tested at the temperature of 100 degrees C in comparison to ambient temperature values using the same operating voltages. Values of up to 0.4 J kg(-1) and 3.1 W kg(-1) were achieved for the work and power outputs per mass, respectively, on a silicone elastomer driven with a voltage of 1.5 kV at a temperature of 100 degrees C.},
  language  = {en}
}
@article{PoudelTichyBruegmannetal.2020,
  author    = {Poudel, Amit and Tichy, Wolfgang and Br{\"u}gmann, Bernd and Dietrich, Tim},
  title     = {Increasing the accuracy of binary neutron star simulations with an improved vacuum treatment},
  series = {Physical review : D, Particles, fields, gravitation, and cosmology},
  volume    = {102},
  journal   = {Physical review : D, Particles, fields, gravitation, and cosmology},
  number    = {10},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0010},
  doi       = {10.1103/PhysRevD.102.104014},
  pages     = {16},
  year      = {2020},
  abstract  = {Numerical-relativity simulations are essential for studying the last stages of the binary neutron star coalescence. Unfortunately, for stable simulations there is the need to add an artificial low-density atmosphere. Here we discuss a new framework in which we can effectively set the density surrounding the neutron stars to zero to ensure a more accurate simulation. We test our method with a number of single star test cases and for an equal-mass binary neutron star simulation. While the bulk motion of the system is not influenced, and hence there is no improvement with respect to the emitted gravitational-wave signal, we find that the new approach is superior with respect to mass conservation and it allows a much better tracking of outward moving material. This will allow a more accurate simulation of the ejected material and supports the interpretation of present and future multimessenger observations with more accurate numerical-relativity simulations.},
  language  = {en}
}
@misc{ChengZhangKliemetal.2020,
  author    = {Cheng, Xin and Zhang, Jie and Kliem, Bernhard and T{\"o}r{\"o}k, Tibor and Xing, Chen and Zhou, Zhenjun and Inhester, Bernd and Ding, Mingde},
  title     = {Initiation and early kinematic evolution of solar eruptions},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {2},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51972},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-519720},
  pages     = {22},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{ChengZhangKliemetal.2020,
  author    = {Cheng, Xin and Zhang, Jie and Kliem, Bernhard and T{\"o}r{\"o}k, Tibor and Xing, Chen and Zhou, Zhenjun and Inhester, Bernd and Ding, Mingde},
  title     = {Initiation and early kinematic evolution of solar eruptions},
  series = {The Astrophysical Journal},
  volume    = {894},
  journal   = {The Astrophysical Journal},
  number    = {2},
  publisher = {Cambridge Scientific Publishers},
  address   = {Cambridge},
  issn      = {1055-6796},
  doi       = {10.3847/1538-4357/ab886a},
  pages     = {1 -- 20},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{SeroussiNowickiPayneetal.2020,
  author    = {Seroussi, Helene and Nowicki, Sophie and Payne, Antony J. and Goelzer, Heiko and Lipscomb, William H. and Abe-Ouchi, Ayako and Agosta, Cecile and Albrecht, Torsten and Asay-Davis, Xylar and Barthel, Alice and Calov, Reinhard and Cullather, Richard and Dumas, Christophe and Galton-Fenzi, Benjamin K. and Gladstone, Rupert and Golledge, Nicholas R. and Gregory, Jonathan M. and Greve, Ralf and Hattermann, Tore and Hoffman, Matthew J. and Humbert, Angelika and Huybrechts, Philippe and Jourdain, Nicolas C. and Kleiner, Thomas and Larour, Eric and Leguy, Gunter R. and Lowry, Daniel P. and Little, Chistopher M. and Morlighem, Mathieu and Pattyn, Frank and Pelle, Tyler and Price, Stephen F. and Quiquet, Aurelien and Reese, Ronja and Schlegel, Nicole-Jeanne and Shepherd, Andrew and Simon, Erika and Smith, Robin S. and Straneo, Fiammetta and Sun, Sainan and Trusel, Luke D. and Van Breedam, Jonas and van de Wal, Roderik S. W. and Winkelmann, Ricarda and Zhao, Chen and Zhang, Tong and Zwinger, Thomas},
  title     = {ISMIP6 Antarctica},
  series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
  volume    = {14},
  journal   = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
  number    = {9},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1994-0416},
  doi       = {10.5194/tc-14-3033-2020},
  pages     = {3033 -- 3070},
  year      = {2020},
  abstract  = {Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and assess the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimates of the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes, forcings employed and initial states of ice sheet models. This study presents results from ice flow model simulations from 13 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100 as part of the Ice Sheet Model Intercomparison for CMIP6 (ISMIP6). They are forced with outputs from a subset of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), representative of the spread in climate model results. Simulations of the Antarctic ice sheet contribution to sea level rise in response to increased warming during this period varies between 7:8 and 30.0 cm of sea level equivalent (SLE) under Representative Concentration Pathway (RCP) 8.5 scenario forcing. These numbers are relative to a control experiment with constant climate conditions and should therefore be added to the mass loss contribution under climate conditions similar to present-day conditions over the same period. The simulated evolution of the West Antarctic ice sheet varies widely among models, with an overall mass loss, up to 18.0 cm SLE, in response to changes in oceanic conditions. East Antarctica mass change varies between 6 :1 and 8.3 cm SLE in the simulations, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional simulated mass loss of 28mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the climate forcing, the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 climate models show an additional mass loss of 0 and 3 cm of SLE on average compared to simulations done under present-day conditions for the two CMIP5 forcings used and display limited mass gain in East Antarctica.},
  language  = {en}
}
@article{ChigarevKazakovPikovsky2020,
  author    = {Chigarev, Vladimir and Kazakov, Alexey and Pikovsky, Arkady},
  title     = {Kantorovich-Rubinstein-Wasserstein distance between overlapping attractor and repeller},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {30},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {7},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {1054-1500},
  doi       = {10.1063/5.0007230},
  pages     = {10},
  year      = {2020},
  abstract  = {We consider several examples of dynamical systems demonstrating overlapping attractor and repeller. These systems are constructed via introducing controllable dissipation to prototypic models with chaotic dynamics (Anosov cat map, Chirikov standard map, and incompressible three-dimensional flow of the ABC-type on a three-torus) and ergodic non-chaotic behavior (skew-shift map). We employ the Kantorovich-Rubinstein-Wasserstein distance to characterize the difference between the attractor and the repeller, in dependence on the dissipation level.},
  language  = {en}
}
@article{AryaJelkenLomadzeetal.2020,
  author    = {Arya, Pooja and Jelken, Joachim and Lomadze, Nino and Santer, Svetlana and Bekir, Marek},
  title     = {Kinetics of photo-isomerization of azobenzene containing surfactants},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry},
  volume    = {152},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry},
  number    = {2},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.5135913},
  pages     = {10},
  year      = {2020},
  abstract  = {We report on photoisomerization kinetics of azobenzene containing surfactants in aqueous solution. The surfactant molecule consists of a positively charged trimethylammonium bromide head group, a hydrophobic spacer connecting via 6 to 10 CH2 groups to the azobenzene unit, and the hydrophobic tail of 1 and 3CH(2) groups. Under exposure to light, the azobenzene photoisomerizes from more stable trans- to metastable cis-state, which can be switched back either thermally in dark or by illumination with light of a longer wavelength. The surfactant isomerization is described by a kinetic model of a pseudo first order reaction approaching equilibrium, where the intensity controls the rate of isomerization until the equilibrated state. The rate constants of the trans-cis and cis-trans photoisomerization are calculated as a function of several parameters such as wavelength and intensity of light, the surfactant concentration, and the length of the hydrophobic tail. The thermal relaxation rate from cis- to trans-state is studied as well. The surfactant isomerization shows a different kinetic below and above the critical micellar concentration of the trans isomer due to steric hindrance within the densely packed micelle but does not depend on the spacer length.},
  language  = {en}
}
@article{RuedigerSchultz2020,
  author    = {R{\"u}diger, G{\"u}nther and Schultz, Manfred},
  title     = {Large-scale dynamo action of magnetized Taylor-Couette flows},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {493},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {1},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0035-8711},
  doi       = {10.1093/mnras/staa293},
  pages     = {1249 -- 1260},
  year      = {2020},
  abstract  = {A conducting Taylor-Couette flow with quasi-Keplerian rotation law containing a toroidal magnetic field serves as a mean-field dynamo model of the Tayler-Spruit type. The flows are unstable against non-axisymmetric perturbations which form electromotive forces defining a effect and eddy diffusivity. If both degenerated modes with m = +/- 1 are excited with the same power then the global a effect vanishes and a dynamo cannot work. It is shown, however, that the Tayler instability produces finite alpha effects if only an isolated mode is considered but this intrinsic helicity of the single-mode is too low for an alpha(2) dynamo. Moreover, an alpha Omega dynamo model with quasi-Keplerian rotation requires a minimum magnetic Reynolds number of rotation of Rm similar or equal to 2000 to work. Whether it really works depends on assumptions about the turbulence energy. For a steeper-than-quadratic dependence of the turbulence intensity on the magnetic field, however, dynamos are only excited if the resulting magnetic eddy diffusivity approximates its microscopic value, eta(T) similar or equal to eta. By basically lower or larger eddy diffusivities the dynamo instability is suppressed.},
  language  = {en}
}
@article{CapałaPadashChechkinetal.2020,
  author    = {Capała, Karol and Padash, Amin and Chechkin, Aleksei V. and Shokri, Babak and Metzler, Ralf and Dybiec, Bartłomiej},
  title     = {Levy noise-driven escape from arctangent potential wells},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {30},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {12},
  publisher = {American Institute of Physics},
  address   = {Woodbury, NY},
  issn      = {1054-1500},
  doi       = {10.1063/5.0021795},
  pages     = {15},
  year      = {2020},
  abstract  = {The escape from a potential well is an archetypal problem in the study of stochastic dynamical systems, representing real-world situations from chemical reactions to leaving an established home range in movement ecology. Concurrently, Levy noise is a well-established approach to model systems characterized by statistical outliers and diverging higher order moments, ranging from gene expression control to the movement patterns of animals and humans. Here, we study the problem of Levy noise-driven escape from an almost rectangular, arctangent potential well restricted by two absorbing boundaries, mostly under the action of the Cauchy noise. We unveil analogies of the observed transient dynamics to the general properties of stationary states of Levy processes in single-well potentials. The first-escape dynamics is shown to exhibit exponential tails. We examine the dependence of the escape on the shape parameters, steepness, and height of the arctangent potential. Finally, we explore in detail the behavior of the probability densities of the first-escape time and the last-hitting point.},
  language  = {en}
}
@article{XuDengSandev2020,
  author    = {Xu, Pengbo and Deng, Weihua and Sandev, Trifce},
  title     = {Levy walk with parameter dependent velocity},
  series = {Journal of physics : A, Mathematical and theoretical},
  volume    = {53},
  journal   = {Journal of physics : A, Mathematical and theoretical},
  number    = {11},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1751-8113},
  doi       = {10.1088/1751-8121/ab7420},
  pages     = {26},
  year      = {2020},
  abstract  = {To analyze stochastic processes, one often uses integral transform (Fourier and Laplace) methods. However, for the time-space coupled cases, e.g. the Levy walk, sometimes the integral transform method may fail. Here we provide a Hermite polynomial expansion approach, being complementary to the integral transform method, to the Levy walk. Two approaches are compared for some already known results. We also consider the generalized Levy walk with parameter dependent velocity. Namely, we consider the Levy walk with velocity which depends on the walking length or on the duration of each step. Some interesting features of the generalized Levy walk are observed, including the special shapes of the probability density function, the first passage time distributions, and various diffusive behaviors of the mean squared displacement.},
  language  = {en}
}
@article{AryaJelkenFeldmannetal.2020,
  author    = {Arya, Pooja and Jelken, Joachim and Feldmann, David and Lomadze, Nino and Santer, Svetlana},
  title     = {Light driven diffusioosmotic repulsion and attraction of colloidal particles},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {152},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {19},
  publisher = {American Institute of Physics},
  address   = {Melville, NY},
  issn      = {0021-9606},
  doi       = {10.1063/5.0007556},
  pages     = {10},
  year      = {2020},
  abstract  = {In this paper, we introduce the phenomenon of light driven diffusioosmotic long-range attraction and repulsion of porous particles under irradiation with UV light. The change in the inter-particle interaction potential is governed by flow patterns generated around single colloids and results in reversible aggregation or separation of the mesoporous silica particles that are trapped at a solid surface. The range of the interaction potential extends to several times the diameter of the particle and can be adjusted by varying the light intensity. The "fuel" of the process is a photosensitive surfactant undergoing photo-isomerization from a more hydrophobic trans-state to a rather hydrophilic cis-state. The surfactant has different adsorption affinities to the particles depending on the isomerization state. The trans-isomer, for example, tends to accumulate in the negatively charged pores of the particles, while the cis-isomer prefers to remain in the solution. This implies that when under UV irradiation cis-isomers are being formed within the pores, they tend to diffuse out readily and generate an excess concentration near the colloid's outer surface, ultimately resulting in the initiation of diffusioosmotic flow. The direction of the flow depends strongly on the dynamic redistribution of the fraction of trans- and cis-isomers near the colloids due to different kinetics of photo-isomerization within the pores as compared to the bulk. The unique feature of the mechanism discussed in the paper is that the long-range mutual repulsion but also the attraction can be tuned by convenient external optical stimuli such as intensity so that a broad variety of experimental situations for manipulation of a particle ensemble can be realized.},
  language  = {en}
}
@article{ToenjesPikovsky2020,
  author    = {T{\"o}njes, Ralf and Pikovsky, Arkady},
  title     = {Low-dimensional description for ensembles of identical phase oscillators subject to Cauchy noise},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {102},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  number    = {5},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.102.052315},
  pages     = {5},
  year      = {2020},
  abstract  = {We study ensembles of globally coupled or forced identical phase oscillators subject to independent white Cauchy noise. We demonstrate that if the oscillators are forced in several harmonics, stationary synchronous regimes can be exactly described with a finite number of complex order parameters. The corresponding distribution of phases is a product of wrapped Cauchy distributions. For sinusoidal forcing, the Ott-Antonsen low-dimensional reduction is recovered.},
  language  = {en}
}
@article{XuZhouMetzleretal.2020,
  author    = {Xu, Pengbo and Zhou, Tian and Metzler, Ralf and Deng, Weihua},
  title     = {L{\´e}vy walk dynamics in an external harmonic potential},
  series = {Physical review : E, Statistical, nonlinear, and soft matter physics},
  volume    = {101},
  journal   = {Physical review : E, Statistical, nonlinear, and soft matter physics},
  number    = {6},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.101.062127},
  pages     = {12},
  year      = {2020},
  abstract  = {Levy walks (LWs) are spatiotemporally coupled random-walk processes describing superdiffusive heat conduction in solids, propagation of light in disordered optical materials, motion of molecular motors in living cells, or motion of animals, humans, robots, and viruses. We here investigate a key feature of LWs-their response to an external harmonic potential. In this generic setting for confined motion we demonstrate that LWs equilibrate exponentially and may assume a bimodal stationary distribution. We also show that the stationary distribution has a horizontal slope next to a reflecting boundary placed at the origin, in contrast to correlated superdiffusive processes. Our results generalize LWs to confining forces and settle some longstanding puzzles around LWs.},
  language  = {en}
}
@article{QuadeIseleAbel2020,
  author    = {Quade, Markus and Isele, Thomas and Abel, Markus},
  title     = {Machine learning control},
  series = {Physica : D, Nonlinear phenomena},
  volume    = {412},
  journal   = {Physica : D, Nonlinear phenomena},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0167-2789},
  doi       = {10.1016/j.physd.2020.132582},
  pages     = {11},
  year      = {2020},
  abstract  = {Recently, the term explainable AI came into discussion as an approach to produce models from artificial intelligence which allow interpretation. For a long time, symbolic regression has been used to produce explainable and mathematically tractable models. In this contribution, we extend previous work on symbolic regression methods to infer the optimal control of a dynamical system given one or several optimization criteria, or cost functions. In earlier publications, network control was achieved by automated machine learning control using genetic programming. Here, we focus on the subsequent path continuation analysis of the mathematical expressions which result from the machine learning model. In particular, we use AUTO to analyze the solution properties of the controlled oscillator system which served as our model. As a result, we show that there is a considerable advantage of explainable symbolic regression models over less accessible neural networks. In particular, the roadmap of future works may be to integrate such analyses into the optimization loop itself to filter out robust solutions by construction.},
  language  = {en}
}
@article{WangSmithSkroblinetal.2020,
  author    = {Wang, Qiong and Smith, Joel A. and Skroblin, Dieter and Steele, Julian A. and Wolff, Christian Michael and Caprioglio, Pietro and Stolterfoht, Martin and K{\"o}bler, Hans and Turren-Cruz, Silver-Hamill and Li, Meng and Gollwitzer, Christian and Neher, Dieter and Abate, Antonio},
  title     = {Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells},
  series = {Solar RRL},
  volume    = {4},
  journal   = {Solar RRL},
  number    = {9},
  publisher = {WILEY-VCH},
  address   = {Weinheim},
  pages     = {9},
  year      = {2020},
  abstract  = {Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6\% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.},
  language  = {en}
}
@misc{WangSmithSkroblinetal.2020,
  author    = {Wang, Qiong and Smith, Joel A. and Skroblin, Dieter and Steele, Julian A. and Wolff, Christian Michael and Caprioglio, Pietro and Stolterfoht, Martin and K{\"o}bler, Hans and Turren-Cruz, Silver-Hamill and Li, Meng and Gollwitzer, Christian and Neher, Dieter and Abate, Antonio},
  title     = {Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {9},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52537},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525374},
  pages     = {11},
  year      = {2020},
  abstract  = {Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6\% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.},
  language  = {en}
}
@phdthesis{Landau2020,
  author    = {Landau, Livnat},
  title     = {Mechanical stimulation of in-vitro tissue growth using magnetic beads},
  pages     = {112},
  year      = {2020},
  abstract  = {Cells and tissues are sensitive to mechanical forces applied to them. In particular, bone forming cells and connective tissues, composed of cells embedded in fibrous extracellular matrix (ECM), are continuously remodeled in response to the loads they bear. The mechanoresponses of cells embedded in tissue include proliferation, differentiation, apoptosis, internal signaling between cells, and formation and resorption of tissue. Experimental in-vitro systems of various designs have demonstrated that forces affect tissue growth, maturation and mineralization. However, the results depended on different parameters such as the type and magnitude of the force applied in each study. Some experiments demonstrated that applied forces increase cell proliferation and inhibit cell maturation rate, while other studies found the opposite effect. When the effect of different magnitudes of forces was compared, some studies showed that higher forces resulted in a cell proliferation increase or differentiation decrease, while other studies observed the opposite trend or no trend at all. In this study, MC3T3-E1 cells, a cell line of pre-osteoblasts (bone forming cells), was used. In this cell line, cell differentiation is known to accelerate after cells stop proliferating, typically at confluency. This makes this cell line an interesting subject for studying the influence of forces on the switch between the proliferation stage of the precursor cell and the differentiation to the mature osteoblasts. A new experimental system was designed to perform systematic investigations of the influence of the type and magnitude of forces on tissue growth. A single well plate contained an array of 80 rectangular pores. Each pore was seeded with MC3T3-E1 cells. The culture medium contained magnetic beads (MBs) of 4.5 μm in diameter that were incorporated into the pre-osteoblast cells. Using an N52 neodymium magnet, forces ranging over three orders of magnitude were applied to MBs incorporated in cells at 10 different distances from the magnet. The amount of formed tissue was assessed after 24 days of culture. The experimental design allowed to obtain data concerning (i) the influence of the type of the force (static, oscillating, no force) on tissue growth; (ii) the influence of the magnitude of force (pN-nN range); (iii) the effect of functionalizing the magnetic beads with the tripeptide Arg-Gly-Asp (RGD). To learn about cell differentiation state, in the final state of the tissue growth experiments, an analysis for the expression of alkaline phosphatase (ALP), a well - known marker of osteoblast differentiation, was performed. The experiments showed that the application of static magnetic forces increased tissue growth compared to control, while oscillating forces resulted in tissue growth reduction. A statistically significant positive correlation was found between the amount of tissue grown and the magnitude of the oscillating magnetic force. A positive but non-significant correlation of the amount of tissue with the magnitude of forces was obtained when static forces were applied. Functionalizing the MBs with RGD peptides and applying oscillating forces resulted in an increase of tissue growth relative to tissues incubated with "plain" epoxy MBs. ALP expression decreased as a function of the magnitude of force both when static and oscillating forces were applied. ALP stain intensity was reduced relative to control when oscillating forces were applied and was not significantly different than control for static forces. The suggested interpretation of the experimental findings is that larger mechanical forces delay cell maturation and keep the pre-osteoblasts in a more proliferative stage characterized by more tissue formed and lower expression of ALP. While the influence of the force magnitude can be well explained by an effect of the force on the switch between proliferation and differentiation, the influence of force type (static or oscillating) is less clear. In particular, it is challenging to reconcile the reduction of tissue formed under oscillating forces as compared to controls with the simultaneous reduction of ALP expression. To better understand this, it may be necessary to refine the staining protocol of the scaffolds and to include the amount and structure of ECM as well as other factors that were not monitored in the experiment and which may influence tissue growth and maturation. The developed experimental system proved well suited for a systematic and efficient study of the mechanoresponsiveness of tissue growth, it allowed a study of the dependence of tissue growth on force magnitude ranging over three orders of magnitude, and a comparison between the effect of static and oscillating forces. Future experiments can explore the multiple parameters that affect tissue growth as a function of the magnitude of the force: by applying different time-dependent forces; by extending the force range studied; or by using different cell lines and manipulating the mechanotransduction in the cells biochemically.},
  language  = {en}
}
@article{SmirnovBerrendorfShpritsetal.2020,
  author    = {Smirnov, Artem and Berrendorf, Max and Shprits, Yuri Y. and Kronberg, Elena A. and Allison, Hayley J. and Aseev, Nikita and Zhelavskaya, Irina and Morley, Steven K. and Reeves, Geoffrey D. and Carver, Matthew R. and Effenberger, Frederic},
  title     = {Medium energy electron flux in earth's outer radiation belt (MERLIN)},
  series = {Space weather : the international journal of research and applications},
  volume    = {18},
  journal   = {Space weather : the international journal of research and applications},
  number    = {11},
  publisher = {American geophysical union, AGU},
  address   = {Washington},
  issn      = {1542-7390},
  doi       = {10.1029/2020SW002532},
  pages     = {20},
  year      = {2020},
  abstract  = {The radiation belts of the Earth, filled with energetic electrons, comprise complex and dynamic systems that pose a significant threat to satellite operation. While various models of electron flux both for low and relativistic energies have been developed, the behavior of medium energy (120-600 keV) electrons, especially in the MEO region, remains poorly quantified. At these energies, electrons are driven by both convective and diffusive transport, and their prediction usually requires sophisticated 4D modeling codes. In this paper, we present an alternative approach using the Light Gradient Boosting (LightGBM) machine learning algorithm. The Medium Energy electRon fLux In Earth's outer radiatioN belt (MERLIN) model takes as input the satellite position, a combination of geomagnetic indices and solar wind parameters including the time history of velocity, and does not use persistence. MERLIN is trained on >15 years of the GPS electron flux data and tested on more than 1.5 years of measurements. Tenfold cross validation yields that the model predicts the MEO radiation environment well, both in terms of dynamics and amplitudes o f flux. Evaluation on the test set shows high correlation between the predicted and observed electron flux (0.8) and low values of absolute error. The MERLIN model can have wide space weather applications, providing information for the scientific community in the form of radiation belts reconstructions, as well as industry for satellite mission design, nowcast of the MEO environment, and surface charging analysis.},
  language  = {en}
}
@phdthesis{Aseev2020,
  author    = {Aseev, Nikita},
  title     = {Modeling and understanding dynamics of charged particles in the Earth's inner magnetosphere},
  doi       = {10.25932/publishup-47921},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-479211},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xxii, 154},
  year      = {2020},
  abstract  = {The Earth's inner magnetosphere is a very dynamic system, mostly driven by the external solar wind forcing exerted upon the magnetic field of our planet. Disturbances in the solar wind, such as coronal mass ejections and co-rotating interaction regions, cause geomagnetic storms, which lead to prominent changes in charged particle populations of the inner magnetosphere - the plasmasphere, ring current, and radiation belts. Satellites operating in the regions of elevated energetic and relativistic electron fluxes can be damaged by deep dielectric or surface charging during severe space weather events. Predicting the dynamics of the charged particles and mitigating their effects on the infrastructure is of particular importance, due to our increasing reliance on space technologies. The dynamics of particles in the plasmasphere, ring current, and radiation belts are strongly coupled by means of collisions and collisionless interactions with electromagnetic fields induced by the motion of charged particles. Multidimensional numerical models simplify the treatment of transport, acceleration, and loss processes of these particles, and allow us to predict how the near-Earth space environment responds to solar storms. The models inevitably rely on a number of simplifications and assumptions that affect model accuracy and complicate the interpretation of the results. In this dissertation, we quantify the processes that control electron dynamics in the inner magnetosphere, paying particular attention to the uncertainties of the employed numerical codes and tools. We use a set of convenient analytical solutions for advection and diffusion equations to test the accuracy and stability of the four-dimensional Versatile Electron Radiation Belt (VERB-4D) code. We show that numerical schemes implemented in the code converge to the analytical solutions and that the VERB-4D code demonstrates stable behavior independent of the assumed time step. The order of the numerical scheme for the convection equation is demonstrated to affect results of ring current and radiation belt simulations, and it is crucially important to use high-order numerical schemes to decrease numerical errors in the model. Using the thoroughly tested VERB-4D code, we model the dynamics of the ring current electrons during the 17 March 2013 storm. The discrepancies between the model and observations above 4.5 Earth's radii can be explained by uncertainties in the outer boundary conditions. Simulation results indicate that the electrons were transported from the geostationary orbit towards the Earth by the global-scale electric and magnetic fields. We investigate how simulation results depend on the input models and parameters. The model is shown to be particularly sensitive to the global electric field and electron lifetimes below 4.5 Earth's radii. The effects of radial diffusion and subauroral polarization streams are also quantified. We developed a data-assimilative code that blends together a convection model of energetic electron transport and loss and Van Allen Probes satellite data by means of the Kalman filter. We show that the Kalman filter can correct model uncertainties in the convection electric field, electron lifetimes, and boundary conditions. It is also demonstrated how the innovation vector - the difference between observations and model prediction - can be used to identify physical processes missing in the model of energetic electron dynamics. We computed radial profiles of phase space density of ultrarelativistic electrons, using Van Allen Probes measurements. We analyze the shape of the profiles during geomagnetically quiet and disturbed times and show that the formation of new local minimums in the radial profiles coincides with the ground observations of electromagnetic ion-cyclotron (EMIC) waves. This correlation indicates that EMIC waves are responsible for the loss of ultrarelativistic electrons from the heart of the outer radiation belt into the Earth's atmosphere.},
  language  = {en}
}
@article{SteppaEgberts2020,
  author    = {Steppa, Constantin and Egberts, Kathrin},
  title     = {Modelling the Galactic very-high-energy gamma-ray source population},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {643},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/202038172},
  pages     = {11},
  year      = {2020},
  abstract  = {Context. The High Energy Stereoscopic System Galactic plane survey (HGPS) is to date the most comprehensive census of Galactic gamma -ray sources at very high energies (VHE; 100 GeV <= E <= 100 TeV). As a consequence of the limited sensitivity of this survey, the 78 detected gamma -ray sources comprise only a small and biased subsample of the overall population. The larger part consists of currently unresolved sources, which contribute to large-scale diffuse emission to a still uncertain amount.Aims. We study the VHE gamma -ray source population in the Milky Way. For this purpose population-synthesis models are derived based on the distributions of source positions, extents, and luminosities.Methods. Several azimuth-symmetric and spiral-arm models are compared for spatial source distribution. The luminosity and radius function of the population are derived from the source properties of the HGPS data set and are corrected for the sensitivity bias of the HGPS. Based on these models, VHE source populations are simulated and the subsets of sources detectable according to the HGPS are compared with HGPS sources.Results. The power-law indices of luminosity and radius functions are determined to range between -1.6 and -1.9 for luminosity and -1.1 and -1.6 for radius. A two-arm spiral structure with central bar is discarded as spatial distribution of VHE sources, while azimuth-symmetric distributions and a distribution following a four-arm spiral structure without bar describe the HGPS data reasonably well. The total number of Galactic VHE sources is predicted to be in the range from 800 to 7000 with a total luminosity and flux of (1.6-6.3) x 10(36) ph s(-1) and (3-15) x 10(-10) ph cm(-2) s(-1), respectively.Conclusions. Depending on the model, the HGPS sample accounts for (68-87)\% of the emission of the population in the scanned region. This suggests that unresolved sources represent a critical component of the diffuse emission measurable in the HGPS. With the foreseen jump in sensitivity of the Cherenkov Telescope Array, the number of detectable sources is predicted to increase by a factor between 5 and 9.},
  language  = {en}
}
@article{CabalarFandinoLierler2020,
  author    = {Cabalar, Pedro and Fandi{\~n}o, Jorge and Lierler, Yuliya},
  title     = {Modular Answer Set Programming as a formal specification language},
  series = {Theory and practice of logic programming},
  volume    = {20},
  journal   = {Theory and practice of logic programming},
  number    = {5},
  publisher = {Cambridge University Press},
  address   = {New York},
  issn      = {1471-0684},
  doi       = {10.1017/S1471068420000265},
  pages     = {767 -- 782},
  year      = {2020},
  abstract  = {In this paper, we study the problem of formal verification for Answer Set Programming (ASP), namely, obtaining aformal proofshowing that the answer sets of a given (non-ground) logic programPcorrectly correspond to the solutions to the problem encoded byP, regardless of the problem instance. To this aim, we use a formal specification language based on ASP modules, so that each module can be proved to capture some informal aspect of the problem in an isolated way. This specification language relies on a novel definition of (possibly nested, first order)program modulesthat may incorporate local hidden atoms at different levels. Then,verifyingthe logic programPamounts to prove some kind of equivalence betweenPand its modular specification.},
  language  = {en}
}
@misc{SchueKopyshevLutzetal.2020,
  author    = {Schu{\´e}, Emmanuelle and Kopyshev, Alexey and Lutz, Jean-Fran{\c{c}}ois and B{\"o}rner, Hans G.},
  title     = {Molecular bottle brushes with positioned selenols},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51618},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-516184},
  pages     = {154 -- 162},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{SchueKopyshevLutzetal.2020,
  author    = {Schu{\´e}, Emmanuelle and Kopyshev, Alexey and Lutz, Jean-Fran{\c{c}}ois and B{\"o}rner, Hans G.},
  title     = {Molecular bottle brushes with positioned selenols},
  series = {Journal of Polymer Science},
  volume    = {58},
  journal   = {Journal of Polymer Science},
  number    = {1},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {2642-4169},
  doi       = {10.1002/pola.29496},
  pages     = {154 -- 162},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@phdthesis{Christ2020,
  author    = {Christ, Simon},
  title     = {Morphological transitions of vesicles exposed to nonuniform spatio-temporal conditions},
  doi       = {10.25932/publishup-48078},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-480788},
  school      = {Universit{\"a}t Potsdam},
  pages     = {viii, 105},
  year      = {2020},
  abstract  = {Giant unilamellar vesicles are an important tool in todays experimental efforts to understand the structure and behaviour of biological cells. Their simple structure allows the isolation of the physical elastic properties of the lipid membrane. A central physical property is the bending energy of the membrane, since the many different shapes of giant vesicles can be obtained by finding the minimum of the bending energy. In the spontaneous curvature model the bending energy is a function of the bending rigidity as well as the mean curvature and an additional parameter called the spontaneous curvature, which describes an internal preference of the lipid-bilayer to bend towards one side or the other. The spontaneous and mean curvature are local properties of the membrane. Additional constraints arise from the conservation of the membrane surface area and the enclosed volume, which are global properties. In this thesis the spontaneous curvature model is used to explain the experimental observation of a periodic shape oscillation of a giant unilamellar vesicle that was filled with a protein complex that periodically binds to and unbinds from the membrane. By assuming that the binding of the proteins to the membrane induces a change in the spontaneous curvature the experimentally observed shapes could successfully be explained. This involves the numerical solution of the differential equations as obtained from the minimization of the bending energy respecting the area and volume constraints, the so called shape equations. Vice versa this approach can be used to estimate the spontaneous curvature from experimentally measurable quantities. The second topic of this thesis is the analysis of concentration gradients in rigid conic membrane compartments. Gradients of an ideal gas due to gravity and gradients generated by the directed stochastic movement of molecular motors along a microtubulus were considered. It was possible to calculate the free energy and the bending energy analytically for the ideal gas. In the case of the non-equilibrium system with molecular motors, the characteristic length of the density profile, the jam-length, and its dependency on the opening angle of the conic compartment have been calculated in the mean-field limit. The mean field results agree qualitatively with stochastic particle simulations.},
  language  = {en}
}
@article{LaingOmel'chenko2020,
  author    = {Laing, Carlo R. and Omel'chenko, Oleh},
  title     = {Moving bumps in theta neuron networks},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {30},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {1054-1500},
  doi       = {10.1063/1.5143261},
  pages     = {11},
  year      = {2020},
  abstract  = {We consider large networks of theta neurons on a ring, synaptically coupled with an asymmetric kernel. Such networks support stable "bumps" of activity, which move along the ring if the coupling kernel is asymmetric. We investigate the effects of the kernel asymmetry on the existence, stability, and speed of these moving bumps using continuum equations formally describing infinite networks. Depending on the level of heterogeneity within the network, we find complex sequences of bifurcations as the amount of asymmetry is varied, in strong contrast to the behavior of a classical neural field model.},
  language  = {en}
}
@phdthesis{Graetz2020,
  author    = {Gr{\"a}tz, Fabio M.},
  title     = {Nonlinear diffusion in granular gases and dense planetary rings},
  school      = {Universit{\"a}t Potsdam},
  pages     = {101},
  year      = {2020},
  abstract  = {Small moonlets or moons embedded in dense planetary rings create S-shaped density modulations called propellers if their masses are smaller than a certain threshold, alternatively they create a circumferential gap in the disk if the embedded body's mass exceeds this threshold (Spahn and Sremčević, 2000). The gravitational perturber scatters the ring particles, depletes the disk's density, and, thus, clears a gap, whereas counteracting viscous diffusion of the ring material has the tendency to close the created gap, thereby forming a propeller. Propeller objects were predicted by Spahn and Sremčević (2000) and Sremčević et al. (2002) and were later discovered by the Cassini space probe (Tiscareno et al., 2006, Sremčević et al., 2007, Tiscareno et al., 2008, and Tiscareno et al., 2010). The ring moons Pan and Daphnis are massive enough to maintain the circumferential Encke and Keeler gaps in Saturn's A ring and were detected by Showalter (1991) and Porco (2005) in Voyager and Cassini images, respectively. In this thesis, a nonlinear axisymmetric diffusion model is developed to describe radial density profiles of circumferential gaps in planetary rings created by embedded moons (Grätz et al., 2018). The model accounts for the gravitational scattering of the ring particles by the embedded moon and for the counteracting viscous diffusion of the ring matter back into the gap. With test particle simulations it is shown that the scattering of the ring particles passing the moon is larger for small impact parameters than estimated by Goldreich and Tremaine (1980). This is especially significant for the modeling of the Keeler gap. The model is applied to the Encke and Keeler gaps with the aim to estimate the shear viscosity of the ring in their vicinities. In addition, the model is used to analyze whether tiny icy moons whose dimensions lie below Cassini's resolution capabilities would be able to cause the poorly understood gap structure of the C ring and the Cassini Division. One of the most intriguing facets of Saturn's rings are the extremely sharp edges of the Encke and Keeler gaps: UVIS-scans of their gap edges show that the optical depth drops from order unity to zero over a range of far less than 100 m, a spatial scale comparable to the ring's vertical extent. This occurs despite the fact that the range over which a moon transfers angular momentum onto the ring material is much larger. Borderies et al. (1982, 1989) have shown that this striking feature is likely related to the local reversal of the usually outward-directed viscous transport of angular momentum in strongly perturbed regions. We have revised the Borderies et al. (1989) model using a granular flow model to define the shear and bulk viscosities, ν and ζ, in order to incorporate the angular momentum flux reversal effect into the axisymmetric diffusion model for circumferential gaps presented in this thesis (Grätz et al., 2019). The sharp Encke and Keeler gap edges are modeled and conclusions regarding the shear and bulk viscosities of the ring are discussed. Finally, we explore the question of whether the radial density profile of the central and outer A ring, recently measured by Tiscareno and Harris (2018) in the highest resolution to date, and in particular, the sharp outer A ring edge can be modeled consistently from the balance of gravitational scattering by several outer moons and the mass and momentum transport. To this aim, the developed model is extended to account for the inward drifts caused by multiple discrete and overlapping resonances with multiple outer satellites and is then used to hydrodynamically simulate the normalized surface mass density profile of the A ring. This section of the thesis is based on studies by Tajeddine et al. (2017a) who recently discussed the common misconception that the 7:6 resonance with Janus alone maintains the outer A ring edge, showing that the combined effort of several resonances with several outer moons is required to confine the A ring as observed by the Cassini spacecraft.},
  language  = {en}
}
@article{Omelʹchenko2020,
  author    = {Omelʹchenko, Oleh E.},
  title     = {Nonstationary coherence-incoherence patterns in nonlocally coupled heterogeneous phase oscillators},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {30},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {1054-1500},
  doi       = {10.1063/1.5145259},
  pages     = {8},
  year      = {2020},
  abstract  = {We consider a large ring of nonlocally coupled phase oscillators and show that apart from stationary chimera states, this system also supports nonstationary coherence-incoherence patterns (CIPs). For identical oscillators, these CIPs behave as breathing chimera states and are found in a relatively small parameter region only. It turns out that the stability region of these states enlarges dramatically if a certain amount of spatially uniform heterogeneity (e.g., Lorentzian distribution of natural frequencies) is introduced in the system. In this case, nonstationary CIPs can be studied as stable quasiperiodic solutions of a corresponding mean-field equation, formally describing the infinite system limit. Carrying out direct numerical simulations of the mean-field equation, we find different types of nonstationary CIPs with pulsing and/or alternating chimera-like behavior. Moreover, we reveal a complex bifurcation scenario underlying the transformation of these CIPs into each other. These theoretical predictions are confirmed by numerical simulations of the original coupled oscillator system.},
  language  = {en}
}