@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{SmirnovShpritsAllisonetal.2022, author = {Smirnov, Artem and Shprits, Yuri and Allison, Hayley and Aseev, Nikita and Drozdov, Alexander and Kollmann, Peter and Wang, Dedong and Saikin, Anthony}, title = {Storm-Time evolution of the Equatorial Electron Pitch Angle Distributions in Earth's Outer Radiation Belt}, series = {Frontiers in astronomy and space sciences}, volume = {9}, journal = {Frontiers in astronomy and space sciences}, publisher = {Frontiers Media}, address = {Lausanne}, issn = {2296-987X}, doi = {10.3389/fspas.2022.836811}, pages = {15}, year = {2022}, abstract = {In this study we analyze the storm-time evolution of equatorial electron pitch angle distributions (PADs) in the outer radiation belt region using observations from the Magnetic Electron Ion Spectrometer (MagEIS) instrument aboard the Van Allen Probes in 2012-2019. The PADs are approximated using a sum of the first, third and fifth sine harmonics. Different combinations of the respective coefficients refer to the main PAD shapes within the outer radiation belt, namely the pancake, flat-top, butterfly and cap PADs. We conduct a superposed epoch analysis of 129 geomagnetic storms and analyze the PAD evolution for day and night MLT sectors. PAD shapes exhibit a strong energy-dependent response. At energies of tens of keV, the PADs exhibit little variation throughout geomagnetic storms. Cap PADs are mainly observed at energies < 300 keV, and their extent in L shrinks with increasing energy. The cap distributions transform into the pancake PADs around the main phase of the storm on the nightside, and then come back to their original shapes during the recovery phase. At higher energies on the dayside, the PADs are mainly pancake during pre-storm conditions and become more anisotropic during the main phase. The quiet-time butterfly PADs can be observed on the nightside at L> 5.6. During the main phase, butterfly PADs have stronger 90 degrees-minima and can be observed at lower L-shells (down to L = 5), then transitioning into flat-top PADs at L similar to 4.5 - 5 and pancake PADs at L < 4.5. The resulting PAD coefficients for different energies, locations and storm epochs can be used to test the wave models and physics-based radiation belt codes in terms of pitch angle distributions.}, language = {en} } @article{SmithBarlowRosenthaletal.2022, author = {Smith, Bryce A. and Barlow, Brad N. and Rosenthal, Benjamin and Hermes, J. J. and Schaffenroth, Veronika}, title = {Pulse Timing Discovery of a Three-day Companion to the Hot Subdwarf BPM 36430}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {939}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/ac9384}, pages = {6}, year = {2022}, abstract = {Hot subdwarf B stars are core-helium-burning objects that have undergone envelope stripping, likely by a binary companion. Using high-speed photometry from the Transiting Exoplanet Survey Satellite, we have discovered the hot subdwarf BPM 36430 is a hybrid sdBV(rs) pulsator exhibiting several low-amplitude g-modes and a strong p-mode pulsation. The latter shows a clear, periodic variation in its pulse arrival times. Fits to this phase oscillation imply BPM 36430 orbits a barycenter approximately 10 light-seconds away once every 3.1 days. Using the CHIRON echelle spectrograph on the CTIO 1.5 m telescope, we confirm the reflex motion by detecting a radial-velocity variation with semiamplitude, period, and phase in agreement with the pulse timings. We conclude that a white dwarf companion with minimum mass of approximate to 0.42 M (circle dot) orbits BPM 36430. Our study represents only the second time a companion orbiting a pulsating hot subdwarf or white dwarf has been detected from pulse timings and confirmed with radial velocities.}, language = {en} } @article{ManassenJbaraAverbukhetal.2022, author = {Manassen, Yishay and Jbara, Moamen and Averbukh, Michael and Hazan, Zion and Henkel, Carsten and Horovitz, Baruch}, title = {Tunnel current noise spectra of spins in individual dimers of molecular radicals}, series = {Physical review : B, Condensed matter and materials physics}, volume = {105}, journal = {Physical review : B, Condensed matter and materials physics}, number = {23}, publisher = {American Physical Society}, address = {College Park}, issn = {2469-9950}, doi = {10.1103/PhysRevB.105.235438}, pages = {9}, year = {2022}, abstract = {We report the detection of electron spin resonance (ESR) in individual dimers of the stable free radical 2,2,6,6tetramethyl-piperidine-1-oxyl (TEMPO). ESR is measured by the current fluctuations in a scanning tunneling microscope (ESR-STM method). The multipeak power spectra, distinct from macroscopic data, are assigned to dimers having exchange and Dzyaloshinskii-Moriya interactions in the presence of spin-orbit coupling. These interactions are generated in our model by interfering electronic tunneling pathways from tip to sample via the dimer???s two molecules. This is the first demonstration that tunneling via two spins is a valid mechanism of the ESR-STM method.}, language = {en} } @article{ZeuschnerWangDebetal.2022, author = {Zeuschner, Steffen Peer and Wang, Xi-Guang and Deb, Marwan and Popova, Elena and Malinowski, Gregory and Hehn, Michel and Keller, Niels and Berakdar, Jamal and Bargheer, Matias}, title = {Standing spin wave excitation in Bi}, series = {Physical review : B, Condensed matter and materials physics}, volume = {106}, journal = {Physical review : B, Condensed matter and materials physics}, number = {13}, publisher = {American Physical Society}, address = {College Park}, issn = {2469-9950}, doi = {10.1103/PhysRevB.106.134401}, pages = {9}, year = {2022}, abstract = {Based on micromagnetic simulations and experimental observations of the magnetization and lattice dynamics after the direct optical excitation of the magnetic insulator Bi : YIG or indirect excitation via an optically opaque Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy and magneto-elastic coupling. The strain and temperature of the lattice are quantified via modeling ultrafast x-ray diffraction data. Measurements of the time-resolved magneto-optical Kerr effect agree well with the magnetization dynamics simulated according to the excitation via two mechanisms: the magneto-elastic coupling to the experimentally verified strain dynamics and the ultrafast temperature-induced transient change in the magnetic anisotropy. The numerical modeling proves that, for direct excitation, both mechanisms drive the fundamental mode with opposite phase. The relative ratio of standing spin wave amplitudes of higher-order modes indicates that both mechanisms are substantially active.}, language = {en} } @article{LaquaiSchauppGriescheetal.2022, author = {Laquai, Ren{\´e} and Schaupp, Thomas and Griesche, Axel and M{\"u}ller, Bernd R. and Kupsch, Andreas and Hannemann, Andreas and Kannengiesser, Thomas and Bruno, Giovanni}, title = {Quantitative analysis of hydrogen-assisted microcracking in duplex stainless steel through X-ray refraction 3D imaging}, series = {Advanced engineering materials}, volume = {24}, journal = {Advanced engineering materials}, number = {6}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1527-2648}, doi = {10.1002/adem.202101287}, pages = {10}, year = {2022}, abstract = {While the problem of the identification of mechanisms of hydrogen-assisted damage has and is being thoroughly studied, the quantitative analysis of such damage still lacks suitable tools. In fact, while, for instance, electron microscopy yields excellent characterization, the quantitative analysis of damage requires at the same time large field-of-views and high spatial resolution. Synchrotron X-ray refraction techniques do possess both features. Herein, it is shown how synchrotron X-ray refraction computed tomography (SXRCT) can quantify damage induced by hydrogen embrittlement in a lean duplex steel, yielding results that overperform even those achievable by synchrotron X-ray absorption computed tomography. As already reported in the literature, but this time using a nondestructive technique, it is shown that the hydrogen charge does not penetrate to the center of tensile specimens. By the comparison between virgin and hydrogen-charged specimens, it is deduced that cracks in the specimen bulk are due to the rolling process rather than hydrogen-assisted. It is shown that (micro)cracks propagate from the surface of tensile specimens to the interior with increasing applied strain, and it is deduced that a significant crack propagation can only be observed short before rupture.}, language = {en} } @article{GuggenbergerChechkinMetzler2022, author = {Guggenberger, Tobias and Chechkin, Aleksei and Metzler, Ralf}, title = {Absence of stationary states and non-Boltzmann distributions of fractional Brownian motion in shallow external potentials}, series = {New journal of physics : the open-access journal for physics}, volume = {24}, journal = {New journal of physics : the open-access journal for physics}, number = {7}, publisher = {Dt. Physikalische Ges.}, address = {[Bad Honnef]}, issn = {1367-2630}, doi = {10.1088/1367-2630/ac7b3c}, pages = {18}, year = {2022}, abstract = {We study the diffusive motion of a particle in a subharmonic potential of the form U(x) = |x|( c ) (0 < c < 2) driven by long-range correlated, stationary fractional Gaussian noise xi ( alpha )(t) with 0 < alpha <= 2. In the absence of the potential the particle exhibits free fractional Brownian motion with anomalous diffusion exponent alpha. While for an harmonic external potential the dynamics converges to a Gaussian stationary state, from extensive numerical analysis we here demonstrate that stationary states for shallower than harmonic potentials exist only as long as the relation c > 2(1 - 1/alpha) holds. We analyse the motion in terms of the mean squared displacement and (when it exists) the stationary probability density function. Moreover we discuss analogies of non-stationarity of Levy flights in shallow external potentials.}, language = {en} } @article{BasnarkovTomovskiSandevetal.2022, author = {Basnarkov, Lasko and Tomovski, Igor and Sandev, Trifce and Kocarev, Ljupčo}, title = {Non-Markovian SIR epidemic spreading model of COVID-19}, series = {Chaos, solitons \& fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science}, volume = {160}, journal = {Chaos, solitons \& fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science}, publisher = {Elsevier}, address = {Oxford [u.a.]}, issn = {0960-0779}, doi = {10.1016/j.chaos.2022.112286}, pages = {8}, year = {2022}, abstract = {We introduce non-Markovian SIR epidemic spreading model inspired by the characteristics of the COVID-19, by considering discrete-and continuous-time versions. The distributions of infection intensity and recovery period may take an arbitrary form. By taking corresponding choice of these functions, it is shown that the model reduces to the classical Markovian case. The epidemic threshold is analytically determined for arbitrary functions of infectivity and recovery and verified numerically. The relevance of the model is shown by modeling the first wave of the epidemic in Italy, Spain and the UK, in the spring, 2020.}, language = {en} } @article{DieterichLindemannMoskoppetal.2022, author = {Dieterich, Peter and Lindemann, Otto and Moskopp, Mats Leif and Tauzin, Sebastien and Huttenlocher, Anna and Klages, Rainer and Chechkin, Aleksei V. and Schwab, Albrecht}, title = {Anomalous diffusion and asymmetric tempering memory in neutrophil chemotaxis}, series = {PLoS Computational Biology : a new community journal}, volume = {18}, journal = {PLoS Computational Biology : a new community journal}, number = {5}, publisher = {PLoS}, address = {San Fransisco}, issn = {1553-734X}, doi = {10.1371/journal.pcbi.1010089}, pages = {26}, year = {2022}, abstract = {Neutrophil granulocytes are essential for the first host defense. After leaving the blood circulation they migrate efficiently towards sites of inflammation. They are guided by chemoattractants released from cells within the inflammatory foci. On a cellular level, directional migration is a consequence of cellular front-rear asymmetry which is induced by the concentration gradient of the chemoattractants. The generation and maintenance of this asymmetry, however, is not yet fully understood. Here we analyzed the paths of chemotacting neutrophils with different stochastic models to gain further insight into the underlying mechanisms. Wildtype chemotacting neutrophils show an anomalous superdiffusive behavior. CXCR2 blockade and TRPC6-knockout cause the tempering of temporal correlations and a reduction of chemotaxis. Importantly, such tempering is found both in vitro and in vivo. These findings indicate that the maintenance of anomalous dynamics is crucial for chemotactic behavior and the search efficiency of neutrophils. The motility of neutrophils and their ability to sense and to react to chemoattractants in their environment are of central importance for the innate immunity. Neutrophils are guided towards sites of inflammation following the activation of G-protein coupled chemoattractant receptors such as CXCR2 whose signaling strongly depends on the activity of Ca2+ permeable TRPC6 channels. It is the aim of this study to analyze data sets obtained in vitro (murine neutrophils) and in vivo (zebrafish neutrophils) with a stochastic mathematical model to gain deeper insight into the underlying mechanisms. The model is based on the analysis of trajectories of individual neutrophils. Bayesian data analysis, including the covariances of positions for fractional Brownian motion as well as for exponentially and power-law tempered model variants, allows the estimation of parameters and model selection. Our model-based analysis reveals that wildtype neutrophils show pure superdiffusive fractional Brownian motion. This so-called anomalous dynamics is characterized by temporal long-range correlations for the movement into the direction of the chemotactic CXCL1 gradient. Pure superdiffusion is absent vertically to this gradient. This points to an asymmetric 'memory' of the migratory machinery, which is found both in vitro and in vivo. CXCR2 blockade and TRPC6-knockout cause tempering of temporal correlations in the chemotactic gradient. This can be interpreted as a progressive loss of memory, which leads to a marked reduction of chemotaxis and search efficiency of neutrophils. In summary, our findings indicate that spatially differential regulation of anomalous dynamics appears to play a central role in guiding efficient chemotactic behavior.}, language = {en} } @article{LaiLuoZwirneretal.2022, author = {Lai, Huagui and Luo, Jincheng and Zwirner, Yannick and Olthof, Selina and Wieczorek, Alexander and Ye, Fangyuan and Jeangros, Quentin and Yin, Xinxing and Akhundova, Fatima and Ma, Tianshu and He, Rui and Kothandaraman, Radha K. and Chin, Xinyu and Gilshtein, Evgeniia and Muller, Andre and Wang, Changlei and Thiesbrummel, Jarla and Siol, Sebastian and Prieto, Jose Marquez and Unold, Thomas and Stolterfoht, Martin and Chen, Cong and Tiwari, Ayodhya N. and Zhao, Dewei and Fu, Fan}, title = {High-performance flexible all-Perovskite tandem solar cells with reduced V-OC-deficit in wide-bandgap subcell}, series = {Advanced energy materials}, volume = {12}, journal = {Advanced energy materials}, number = {45}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1614-6832}, doi = {10.1002/aenm.202202438}, pages = {12}, year = {2022}, abstract = {Among various types of perovskite-based tandem solar cells (TSCs), all-perovskite TSCs are of particular attractiveness for building- and vehicle-integrated photovoltaics, or space energy areas as they can be fabricated on flexible and lightweight substrates with a very high power-to-weight ratio. However, the efficiency of flexible all-perovskite tandems is lagging far behind their rigid counterparts primarily due to the challenges in developing efficient wide-bandgap (WBG) perovskite solar cells on the flexible substrates as well as their low open-circuit voltage (V-OC). Here, it is reported that the use of self-assembled monolayers as hole-selective contact effectively suppresses the interfacial recombination and allows the subsequent uniform growth of a 1.77 eV WBG perovskite with superior optoelectronic quality. In addition, a postdeposition treatment with 2-thiopheneethylammonium chloride is employed to further suppress the bulk and interfacial recombination, boosting the V-OC of the WBG top cell to 1.29 V. Based on this, the first proof-of-concept four-terminal all-perovskite flexible TSC with a power conversion efficiency of 22.6\% is presented. When integrating into two-terminal flexible tandems, 23.8\% flexible all-perovskite TSCs with a superior V-OC of 2.1 V is achieved, which is on par with the V-OC reported on the 28\% all-perovskite tandems grown on the rigid substrate.}, language = {en} }