@article{RamanVenkatesanWuebbenhorstGerhard2022, author = {Raman Venkatesan, Thulasinath and W{\"u}bbenhorst, Michael and Gerhard, Reimund}, title = {Structure-property relationships in three-phase relaxor-ferroelectric terpolymers}, series = {Ferroelectrics}, volume = {586}, journal = {Ferroelectrics}, number = {1}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0015-0193}, doi = {10.1080/00150193.2021.2014260}, pages = {60 -- 81}, year = {2022}, abstract = {Poly(vinylidenefluoride-trifluoroethylene)-based (P(VDF-TrFE)-based) terpolymers represent a new class of electroactive polymer materials that are relaxor-ferroelectric (RF) polymers and that offer unique and attractive property combinations in comparison with conventional ferroelectric polymers. The RF state is achieved by introducing a fluorine-containing termonomer as a "defect" into the ferroelectric P(VDF-TrFE) copolymer, which reduces the interaction between the VDF/TrFE dipoles. The resulting terpolymer exhibits a low Curie transition temperature and small remanent and coercive fields yielding a slim hysteresis loop that is typical for RF materials. Though the macroscopic behavior is similar to RF ceramics, the mechanisms of relaxor ferroelectricity in semi-crystalline polymers are different and not fully understood yet. Structure-property relationships play an important role in RF terpolymers, as they govern the final RF properties. Hence, a review of important characteristics, previous studies and relevant developments of P(VDF-TrFE)-based terfluoropolymers with either chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE) as the termonomer is deemed useful. The role of the termonomer and of its composition, as well as the effects of the processing conditions on the semi-crystalline structure which in turn affects the final RF properties are discussed in detail. In addition, the presence of noteworthy transition(s) in the mid-temperature range and the influence of preparation conditions on those transitions are reviewed. A better understanding of the fundamental aspects affecting the semi-crystalline structures will help to elucidate the nature of RF activity in VDF-based terpolymers and also help to further improve their applications-relevant electroactive properties.}, language = {en} } @article{RamosLariosToalaRodriguezGonzalezetal.2022, author = {Ramos-Larios, Gerardo and Toala, Jes{\´u}s Alberto and Rodriguez-Gonzalez, Janis B. and Guerrero, Martin A. and Gomez-Gonzalez, V{\´i}ctor Mauricio Alfonso}, title = {Rings and arcs around evolved stars - III. Physical conditions of the ring-like structures in the planetary nebula IC 4406 revealed by MUSE}, series = {Monthly notices of the Royal Astronomical Society}, volume = {513}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stac605}, pages = {2862 -- 2868}, year = {2022}, abstract = {We present the analysis of Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least five ring-like structures north and south of the main nebula of IC4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (n(e)), and temperature (T-e). The rings are found to have similar T-e as the rim of the main nebula, but smaller n(e). Ratios between different ionic species suggest that the rings of IC4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC 6543, the Cat's Eye Nebula.}, language = {en} } @article{RashtiFabbriBruegmannetal.2022, author = {Rashti, Alireza and Fabbri, Francesco Maria and Br{\"u}gmann, Bernd and Chaurasia, Swami Vivekanandji and Dietrich, Tim and Ujevic, Maximiliano and Tichy, Wolfgang}, title = {New pseudospectral code for the construction of initial data}, series = {Physical review D}, volume = {105}, journal = {Physical review D}, number = {10}, publisher = {American Physical Society}, address = {College Park}, issn = {2470-0010}, doi = {10.1103/PhysRevD.105.104027}, pages = {18}, year = {2022}, abstract = {Numerical studies of the dynamics of gravitational systems, e.g., black hole-neutron star systems, require physical and constraint-satisfying initial data. In this article, we present the newly developed pseudospectral code ELLIPTICA, an infrastructure for construction of initial data for various binary and single gravitational systems of all kinds. The elliptic equations under consideration are solved on a single spatial hypersurface of the spacetime manifold. Using coordinate maps, the hypersurface is covered by patches whose boundaries can adapt to the surface of the compact objects. To solve elliptic equations with arbitrary boundary condition, ELLIPTICA deploys a Schur complement domain decomposition method with a direct solver. In this version, we use cubed sphere coordinate maps and the fields are expanded using Chebyshev polynomials of the first kind. Here, we explain the building blocks of ELLIPTICA and the initial data construction algorithm for a black hole-neutron star binary system. We perform convergence tests and evolve the data to validate our results. Within our framework, the neutron star can reach spin values close to breakup with arbitrary direction, while the black hole can have arbitrary spin with dimensionless spin magnitude ∼0.8.}, language = {en} } @article{Regenstein2022, author = {Regenstein, Wolfgang}, title = {Statistische Beschreibung des Resonanzenergietransfers in L{\"o}sungen}, doi = {10.25932/publishup-56500}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-565009}, pages = {23}, year = {2022}, abstract = {In resonance energy transfer, photons are transferred from an excited donor to an acceptor over an interaction distance. According to F{\"o}rster's quantum mechanical theory, this distance can be calculated using the overlap integral of the fluorescence spectrum of the donor and the absorption spectrum of the acceptor. Another possibility of determination is obtained with the help of statistical models, which are compiled in an overview. The distance can be determined by evaluating the extinction curve. In this work, a further statistical variant of the determination of the interaction radius is added and demonstrated in detail using an example.}, language = {de} } @article{Regenstein2022, author = {Regenstein, Wolfgang}, title = {Statistische Beschreibung des Resonanzenergietransfers in L{\"o}sungen}, edition = {2. Version}, doi = {10.25932/publishup-56597}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-565977}, pages = {23}, year = {2022}, abstract = {Beim Resonanzenergietransfer werden Fotonen von einem angeregten Donator {\"u}ber einen Wechselwirkungsabstand auf einen Akzeptor {\"u}bertragen. Nach der quantenmechanischen Theorie von F{\"O}RSTER kann dieser Abstand mit Hilfe des {\"U}berlappungsintegrals von Fluoreszenzspektrum des Donators und Absorp-tionsspektrum des Akzeptors berechnet werden. Eine andere M{\"o}glichkeit der Bestimmung erh{\"a}lt man mit Hilfe von statistischen Modellen, die in einem {\"U}berblick zusammengestellt sind. Dabei kann der Abstand durch Auswertung der L{\"o}schkurve bestimmt werden. In dieser Arbeit wird dazu eine weitere statistische Variante der Bestimmung des Wechselwirkungsradius hinzugef{\"u}gt und an einem Beispiel ausf{\"u}hrlich demonstriert.}, language = {de} } @article{RieseVogelsangSchroederetal.2022, author = {Riese, Josef and Vogelsang, Christoph and Schr{\"o}der, Jan and Borowski, Andreas and Kulgemeyer, Christoph and Reinhold, Peter and Schecker, Horst}, title = {The development of lesson planning skills in the subject of physics}, series = {Zeitschrift f{\"u}r Erziehungswissenschaft}, journal = {Zeitschrift f{\"u}r Erziehungswissenschaft}, number = {4}, publisher = {Springer VS/Springer Fachmedien Wiesbaden GmbH}, address = {Wiesbaden}, issn = {1434-663X}, doi = {10.1007/s11618-022-01112-0}, pages = {843 -- 867}, year = {2022}, abstract = {One main goal of university teacher education is the first acquisition of skills for theory-driven lesson planning. According to models of teachers' professional competence, it is assumed that the acquired professional knowledge represents an essential basis for the development of planning skills. Learning opportunities to apply this professional knowledge often occur in school internships, usually in advanced semesters of teacher education programs. It is also assumed that practical experience within lesson planning supports the formation of professional knowledge. However, the relationship between the extent of professional knowledge and the development of skills to plan a lesson lacks evidence. There is a particular challenge in measuring lesson planning skills both authentically and standardized. To evaluate the mentioned relationship, a longitudinal pre-post-study with prospective physics-teachers (N = 68 in the longitudinal section) was conducted at four German universities. Pre-service physics teachers' skills to plan a lesson were assessed with a standardized performance assessment at the beginning and at the end of a longterm-internship. This assessment consists of planning a physics lesson, conveying Newton's third Law, in a simulated and standardized way with limited time. In addition, content knowledge, pedagogical content knowledge and pedagogical knowledge has been assessed using standardized instruments. Furthermore, additional information about the internship and the amount of learning opportunities was collected at the end of the internship. During the internship, both lesson planning skills and all components of professional knowledge increased. Cross-Lagged-Panel-Analyses reveal that in particular pre-service teachers' pedagogical content knowledge as well as pedagogical knowledge at the beginning of the internship influences the development of lesson planning skills.}, language = {de} } @article{RubioToalaTodtetal.2022, author = {Rubio, Gabriel and Toal{\´a}, Jes{\´u}s Alberto and Todt, Helge Tobias and Sabin, Laurence and Santamar{\´i}a, Edgar and Ramos-Larios, Gerardo and Mart{\´i}n Guerrero, Jos{\´e} David}, title = {Planetary nebulae with Wolf-Rayet-type central stars - IV. NGC 1501 and its mixing layer}, series = {Monthly notices of the Royal Astronomical Society}, volume = {517}, journal = {Monthly notices of the Royal Astronomical Society}, number = {4}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stac3011}, pages = {5166 -- 5179}, year = {2022}, abstract = {Theory predicts that the temperature of the X-ray-emitting gas (similar to 10(6) K) detected from planetary nebulae (PNe) is a consequence of mixing or thermal conduction when in contact with the ionized outer rim (similar to 10(4) K). Gas at intermediate temperatures (similar to 10(5) K) can be used to study the physics of the production of X-ray-emitting gas, via C iv, N v, and O vi ions. Here, we model the stellar atmosphere of the CSPN of NGC 1501 to demonstrate that even this hot H-deficient [WO4]-type star cannot produce these emission lines by photoionization. We use the detection of the C iv lines to assess the physical properties of the mixing region in this PNe in comparison with its X-ray-emitting gas, rendering NGC 1501 only the second PNe with such characterization. We extend our predictions to the hottest [WO1] and cooler [WC5] spectral types and demonstrate that most energetic photons are absorbed in the dense winds of [WR] CSPN and highly ionized species can be used to study the physics behind the production of hot bubbles in PNe. We found that the UV observations of NGC 2452, NGC 6751, and NGC 6905 are consistent with the presence mixing layers and hot bubbles, providing excellent candidates for future X-ray observations.}, language = {en} } @article{RuedigerSchultz2022, author = {R{\"u}diger, G{\"u}nther and Schultz, Manfred}, title = {On the toroidal-velocity antidynamo theorem under the presence of nonuniform electric conductivity}, series = {Astronomische Nachrichten = Astronomical notes}, volume = {343}, journal = {Astronomische Nachrichten = Astronomical notes}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0004-6337}, doi = {10.1002/asna.20224011}, pages = {10}, year = {2022}, abstract = {Laminar electrically conducting Couette flows with the hydrodynamically stable quasi-Keplerian rotation profile and nonuniform conductivity are probed for dynamo instability. In spherical geometry, the equations for the poloidal and the toroidal field components completely decouple, resulting in free decay, regardless of the spatial distribution of the electric conductivity. In cylindrical geometry the poloidal and toroidal components do not decouple, but here also we do not find dynamo excitations for the cases that the electric conductivity only depends on the radius or - much more complex- that it only depends on the azimuthal or the axial coordinate. The transformation of the plane-flow dynamo model of Busse and Wicht (1992) to cylindrical or spherical geometry therefore fails. It is also shown that even the inclusion of axial flows of both directions does not support the dynamo mechanism. The Elsasser toroidal-velocity antidynamo theorem, according to which dynamos without any radial velocity component cannot work, is thus not softened by nonuniform conductivity distributions.}, language = {en} } @article{SachseKappelTirschetal.2022, author = {Sachse, Manuel and Kappel, David and Tirsch, Daniela and Otto, Katharina A.}, title = {Discrete element modeling of aeolian-like morphologies on comet 67P/Churyumov-Gerasimenko}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {662}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/202141296}, pages = {15}, year = {2022}, abstract = {Context. Even after the Rosetta mission, some of the mechanical parameters of comet 67P/Churyumov-Gerasimenko's surface material are still not well constrained. They are needed to improve our understanding of cometary activity or for planning sample return procedures. Aims. We discuss the physical process dominating the formation of aeolian-like surface features in the form of moats and wind taillike bedforms around obstacles and investigate the mechanical and geometrical parameters involved. Methods. By applying the discrete element method (DEM) in a low-gravity environment, we numerically simulated the dynamics of the surface layer particles and the particle stream involved in the formation of aeolian-like morphological features. The material is composed of polydisperse spherical particles that consist of a mixture of dust and water ice, with interparticle forces given by the Hertz contact model, cohesion, friction, and rolling friction. We determined a working set of parameters that enables simulations to be reasonably realistic and investigated morphological changes when modifying these parameters. Results. The aeolian-like surface features are reasonably well reproduced using model materials with a tensile strength on the order of 0.1-1 Pa. Stronger materials and obstacles with round shapes impede the formation of a moat and a wind tail. The integrated dust flux required for the formation of moats and wind tails is on the order of 100 kg m(-2), which, based on the timescale of morphological changes inferred from Rosetta images, translates to a near-surface particle density on the order of 10(-6)-10(-4) kg m(-3). Conclusions. DEM modeling of the aeolian-like surface features reveals complex formation mechanisms that involve both deposition of ejected material and surface erosion. More numerical work and additional in situ measurements or sample return missions are needed to better investigate mechanical parameters of cometary surface material and to understand the mechanics of cometary activity.}, language = {en} } @article{SajediKrivenkovMarchenkoetal.2022, author = {Sajedi, Maryam and Krivenkov, Maxim and Marchenko, Dmitry and Sanchez-Barriga, Jaime and Chandran, Anoop K. and Varykhalov, Andrei and Rienks, Emile D. L. and Aguilera, Irene and Bl{\"u}gel, Stefan and Rader, Oliver}, title = {Is there a polaron signature in Angle-Resolved Photoemission of CsPbBr3?}, series = {Physical review letters}, volume = {128}, journal = {Physical review letters}, number = {17}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.128.176405}, pages = {7}, year = {2022}, abstract = {The formation of large polarons has been proposed as reason for the high defect tolerance, low mobility, low charge carrier trapping, and low nonradiative recombination rates of lead halide perovskites. Recently, direct evidence for large-polaron formation has been reported from a 50\% effective mass enhancement in angle-resolved photoemission of CsPbBr3 over theory for the orthorhombic structure. We present in-depth band dispersion measurements of CsPbBr3 and GW calculations, which lead to similar effective masses at the valence band maximum of 0.203 1 0.016 m0 in experiment and 0.226 m0 in orthorhombic theory. We argue that the effective mass can be explained solely on the basis of electron-electron correlation and largepolaron formation cannot be concluded from photoemission data.}, language = {en} }