@article{PanLiuGouetal.2021, author = {Pan, Hanya and Liu, Rui and Gou, Tingyu and Kliem, Bernhard and Su, Yingna and Chen, Jun and Wang, Yuming}, title = {Pre-eruption splitting of the double-decker structure in a solar filament}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {909}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {Institute of Physics Publ.}, address = {London}, issn = {0004-637X}, doi = {10.3847/1538-4357/abda4e}, pages = {12}, year = {2021}, abstract = {Solar filaments often erupt partially. Although how they split remains elusive, the splitting process has the potential of revealing the filament structure and eruption mechanism. Here we investigate the pre-eruption splitting of an apparently single filament and its subsequent partial eruption on 2012 September 27. The evolution is characterized by three stages with distinct dynamics. During the quasi-static stage, the splitting proceeds gradually for about 1.5 hr, with the upper branch rising at a few kilometers per second and displaying swirling motions about its axis. During the precursor stage that lasts for about 10 minutes, the upper branch rises at tens of kilometers per second, with a pair of conjugated dimming regions starting to develop at its footpoints; with the swirling motions turning chaotic, the axis of the upper branch whips southward, which drives an arc-shaped extreme-ultraviolet front propagating in a similar direction. During the eruption stage, the upper branch erupts with the onset of a C3.7-class two-ribbon flare, while the lower branch remains stable. Judging from the well-separated footpoints of the upper branch from those of the lower one, we suggest that the pre-eruption filament processes a double-decker structure composed of two distinct flux bundles, whose formation is associated with gradual magnetic flux cancellations and converging photospheric flows around the polarity inversion line.}, language = {en} } @article{CampbellKairaliyevaSanteretal.2022, author = {Campbell, Richard and Kairaliyeva, Talmira and Santer, Svetlana and Schneck, Emanuel and Miller, Reinhard}, title = {Direct resolution of the interactions of a hydrocarbon gas with adsorbed surfactant monolayers at the water/air interface using neutron reflectometry}, series = {Colloids and interfaces}, volume = {6}, journal = {Colloids and interfaces}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2504-5377}, doi = {10.3390/colloids6040068}, pages = {12}, year = {2022}, abstract = {We have directly resolved in the present work the interfacial composition during and after the interactions of a saturated atmosphere of oil vapor with soluble surfactant solutions at a planar water/air interface for the first time. Experiments were conducted on interactions of hexane vapor with solutions of alkyltrimethylammonium bromides and sodium dodecyl sulfate to observe the balance between cooperativity and competition of the components at the interface. In all cases, hexane adsorption was strongly enhanced by the presence of the surfactant, even at bulk surfactant concentrations four orders of magnitude below the critical micelle concentration. Cooperativity of the surfactant adsorption was observed only for sodium dodecyl sulfate at intermediate bulk concentrations, yet for all four systems, competition set in at higher concentrations, as hexane adsorption reduced the surfactant surface excess. The data fully supported the complete removal of hexane from the interface following venting of the system to remove the saturated atmosphere of oil vapor. These results help to identify future experiments that would elaborate and could explain the cooperativity of surfactant adsorption, such as on cationic surfactants with short alkyl chains and a broader series of anionic surfactants. This work holds relevance for oil recovery applications with foam, where there is a gas phase saturated with oil vapor.}, language = {en} } @article{SerranoMunozUlbrichtFritschetal.2021, author = {Serrano-Munoz, Itziar and Ulbricht, Alexander and Fritsch, Tobias and Mishurova, Tatiana and Kromm, Arne and Hofmann, Michael and Wimpory, Robert C. and Evans, Alexander and Bruno, Giovanni}, title = {Scanning manufacturing parameters determining the residual stress state in LPBF IN718 small parts}, series = {Advanced engineering materials}, volume = {23}, journal = {Advanced engineering materials}, number = {7}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1438-1656}, doi = {10.1002/adem.202100158}, pages = {13}, year = {2021}, abstract = {The influence of scan strategy on the residual stress (RS) state of an as-built IN718 alloy produced by means of laser powder bed fusion (LPBF) is investigated. Two scan vector rotations (90 degrees-alternation and 67 degrees-rotation), each produced following two different scan vector lengths (long and short), are used to manufacture four rectangular prisms. Neutron diffraction (ND) and laboratory X-ray diffraction (XRD) techniques are used to map the bulk and surface RS state, respectively. The distortion induced upon removal from the baseplate is measured via profilometry. XRD measurements show that the two long scan vector strategies lead to higher RS when compared with the equivalent short scan vector strategies. Also, the 67 degrees-rotation strategies generate lower RS than their 90 degrees-alternation counterparts. Due to the lack of reliable stress-free d0 references, the ND results are analyzed using von Mises stress. In general, ND results show significant RS spatial non-uniformity. A comparison between ND and distortion results indicates that the RS component parallel to the building direction (Z-axis) has a predominant role in the Z-displacement. The use of a stress balance scheme allows to discuss the d0 variability along the length of the specimens, as well as examine the absolute RS state.}, language = {en} } @article{BalcerekBurneckiThapaetal.2022, author = {Balcerek, Michal and Burnecki, Krzysztof and Thapa, Samudrajit and Wylomanska, Agnieszka and Chechkin, Aleksei}, title = {Fractional Brownian motion with random Hurst exponent}, series = {Chaos : an interdisciplinary journal of nonlinear science}, volume = {32}, journal = {Chaos : an interdisciplinary journal of nonlinear science}, number = {9}, publisher = {AIP Publishing}, address = {Melville}, issn = {1054-1500}, doi = {10.1063/5.0101913}, pages = {15}, year = {2022}, abstract = {Fractional Brownian motion, a Gaussian non-Markovian self-similar process with stationary long-correlated increments, has been identified to give rise to the anomalous diffusion behavior in a great variety of physical systems. The correlation and diffusion properties of this random motion are fully characterized by its index of self-similarity or the Hurst exponent. However, recent single-particle tracking experiments in biological cells revealed highly complicated anomalous diffusion phenomena that cannot be attributed to a class of self-similar random processes. Inspired by these observations, we here study the process that preserves the properties of the fractional Brownian motion at a single trajectory level; however, the Hurst index randomly changes from trajectory to trajectory. We provide a general mathematical framework for analytical, numerical, and statistical analysis of the fractional Brownian motion with the random Hurst exponent. The explicit formulas for probability density function, mean-squared displacement, and autocovariance function of the increments are presented for three generic distributions of the Hurst exponent, namely, two-point, uniform, and beta distributions. The important features of the process studied here are accelerating diffusion and persistence transition, which we demonstrate analytically and numerically.}, language = {en} } @article{FornieriZhang2022, author = {Fornieri, Ottavio and Zhang, Heshou}, title = {MHD decomposition explains diffuse 𝛾-ray emission in Cygnus X}, series = {Physical review : D, Particles, fields, gravitation, and cosmology}, volume = {106}, journal = {Physical review : D, Particles, fields, gravitation, and cosmology}, number = {10}, publisher = {American Physical Society}, address = {Ridge, NY}, issn = {2470-0010}, doi = {10.1103/PhysRevD.106.103015}, pages = {8}, year = {2022}, abstract = {Cosmic-ray (CR) diffusion is the result of the interaction of such charged particles against magnetic fluctuations. These fluctuations originate from large-scale turbulence cascading toward smaller spatial scales, decomposed into three different modes, as described by magnetohydrodynamics (MHD) theory. As a consequence, the description of particle diffusion strongly depends on the model describing the injected turbulence. Moreover, the amount of energy assigned to each of the three modes is, in general, not equally divided, which implies that diffusion properties might be different from one region to another. Here, motivated by the detection of different MHD modes inside the Cygnus-X star-forming region, we study the 3D transport of CRs injected by two prominent sources within a two-zone model that represents the distribution of the modes. Then, by convolving the propagated CR distribution with the neutral gas, we are able to explain the 𝛾-ray diffuse emission in the region, observed by the Fermi-LAT and HAWC Collaborations. Such a result represents an important step in the long-standing problem of connecting the CR observables with the microphysics of particle transport.}, language = {en} } @article{ChenSuLiuetal.2021, author = {Chen, Jialin and Su, Yingna and Liu, Rui and Kliem, Bernhard and Zhang, Qingmin and Ji, Haisheng and Liu, Tie}, title = {Partial eruption, confinement, and twist buildup and release of a double-decker filament}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics.}, volume = {923}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics.}, number = {2}, publisher = {Institute of Physics Publ.}, address = {London}, issn = {0004-637X}, doi = {10.3847/1538-4357/ac2ba1}, pages = {16}, year = {2021}, abstract = {We investigate the failed partial eruption of a filament system in NOAA AR 12104 on 2014 July 5, using multiwavelength EUV, magnetogram, and H alpha observations, as well as magnetic field modeling. The filament system consists of two almost co-spatial segments with different end points, both resembling a C shape. Following an ejection and a precursor flare related to flux cancellation, only the upper segment rises and then displays a prominent twisted structure, while rolling over toward its footpoints. The lower segment remains undisturbed, indicating that the system possesses a double-decker structure. The erupted segment ends up with a reverse-C shape, with material draining toward its footpoints, while losing its twist. Using the flux rope insertion method, we construct a model of the source region that qualitatively reproduces key elements of the observed evolution. At the eruption onset, the model consists of a flux rope atop a flux bundle with negligible twist, which is consistent with the observational interpretation that the filament possesses a double-decker structure. The flux rope reaches the critical height of the torus instability during its initial relaxation, while the lower flux bundle remains in stable equilibrium. The eruption terminates when the flux rope reaches a dome-shaped quasi-separatrix layer that is reminiscent of a magnetic fan surface, although no magnetic null is found. The flux rope is destroyed by reconnection with the confining overlying flux above the dome, transferring its twist in the process.}, language = {en} } @article{GostkowskaLeknerKojdaHoffmannetal.2022, author = {Gostkowska-Lekner, Natalia and Kojda, Sandrino Danny and Hoffmann, Jan-Ekkehard and May, Manfred and Huber, Patrick and Habicht, Klaus and Hofmann, Tommy}, title = {Synthesis of organic-inorganic hybrids based on the conjugated polymer P3HT and mesoporous silicon}, series = {Microporous and mesoporous materials : zeolites, clays, carbons and related materials}, volume = {343}, journal = {Microporous and mesoporous materials : zeolites, clays, carbons and related materials}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1387-1811}, doi = {10.1016/j.micromeso.2022.112155}, pages = {6}, year = {2022}, abstract = {Organic-inorganic hybrids are a class of functional materials that combine favorable properties of their constituents to achieve an overall improved performance for a wide range of applications. This article presents the synthesis route for P3HT-porous silicon hybrids for thermoelectric applications. The conjugated polymer P3HT is incorporated into the porous silicon matrix by means of melt infiltration. Gravimetry, sorption isotherms and energy dispersive X-ray spectroscopy (EDX) mapping indicate that the organic molecules occupy more than 50\% of the void space in the inorganic host. We demonstrate that subsequent diffusion-based doping of the confined polymer in a FeCl3 solution increases the electrical conductivity of the hybrid by five orders of magnitude compared to the empty porous silicon host.}, language = {en} } @article{HofmannKojdaHaseebetal.2021, author = {Hofmann, Tommy and Kojda, Sandrino Danny and Haseeb, Haider and Wallacher, Dirk and Sobolev, Oleg and Habicht, Klaus}, title = {Phonons in highly-crystalline mesoporous silicon: the absence of phonon-softening upon structuring silicon on sub-10 nanometer length scales}, series = {Microporous and mesoporous materials : the official journal of the International Zeolite Association}, volume = {312}, journal = {Microporous and mesoporous materials : the official journal of the International Zeolite Association}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1387-1811}, doi = {10.1016/j.micromeso.2020.110814}, pages = {7}, year = {2021}, abstract = {This article presents inelastic thermal neutron scattering experiments probing the phonon dispersion in mesoporous silicon with pores 8 nm across. Scattering studies reveal the energy-momentum relation for transverse and longitudinal phonons along the high symmetry directions , and in the Brillouin zone. The dispersion up to phonon energies of 35 meV unambiguously proves that the phonon group velocities in highly-crystalline silicon are not modified by nanostructuring down to sub-10 nanometer length scales. On these length scales, there is apparently no effect of structuring on the elastic moduli of mesoporous silicon. No evidence can be found for phonon-softening in topologically complex, geometrically disordered mesoporous silicon putting it in contrast to silicon nanotubes and nanoribbons.}, language = {en} } @article{SprengelUlbrichtEvansetal.2021, author = {Sprengel, Maximilian and Ulbricht, Alexander and Evans, Alexander and Kromm, Arne and Sommer, Konstantin and Werner, Tiago and Kelleher, Joanne and Bruno, Giovanni and Kannengießer, Thomas}, title = {Towards the optimization of post-laser powder bed fusion stress-relieve treatments of stainless steel 316L}, series = {Metallurgical and materials transactions. A, Physical metallurgy and materials science}, volume = {52}, journal = {Metallurgical and materials transactions. A, Physical metallurgy and materials science}, number = {12}, publisher = {Springer}, address = {Boston}, issn = {1073-5623}, doi = {10.1007/s11661-021-06472-6}, pages = {5342 -- 5356}, year = {2021}, abstract = {The use of post-processing heat treatments is often considered a necessary approach to relax high-magnitude residual stresses (RS) formed during the layerwise additive manufacturing laser powder bed fusion (LPBF). In this work, three heat treatment strategies using temperatures of 450 degrees C, 800 degrees C, and 900 degrees C are applied to austenitic stainless steel 316L samples manufactured by LPBF. These temperatures encompass the suggested lower and upper bounds of heat treatment temperatures of conventionally processed 316L. The relaxation of the RS is characterized by neutron diffraction (ND), and the associated changes of the microstructure are analyzed using electron backscattered diffraction (EBSD) and scanning electron microscopy (SEM). The lower bound heat treatment variant of 450 degrees C for 4 hours exhibited high tensile and compressive RS. When applying subsequent heat treatments, we show that stress gradients are still observed after applying 800 degrees C for 1 hour but almost completely vanish when applying 900 degrees C for 1 hour. The observed near complete relaxation of the RS appears to be closely related to the evolution of the characteristic subgrain solidification cellular microstructure.}, language = {en} } @article{AryaUmlandtJelkenetal.2021, author = {Arya, Pooja and Umlandt, Maren and Jelken, Joachim and Feldmann, David and Lomadze, Nino and Asmolov, Evgeny S. and Vinogradova, Olga I. and Santer, Svetlana}, title = {Light-induced manipulation of passive and active microparticles}, series = {The European physical journal. E, Soft matter}, volume = {44}, journal = {The European physical journal. E, Soft matter}, number = {4}, publisher = {Springer}, address = {Berlin}, issn = {1292-8941}, doi = {10.1140/epje/s10189-021-00032-x}, pages = {10}, year = {2021}, abstract = {We consider sedimented at a solid wall particles that are immersed in water containing small additives of photosensitive ionic surfactants. It is shown that illumination with an appropriate wavelength, a beam intensity profile, shape and size could lead to a variety of dynamic, both unsteady and steady state, configurations of particles. These dynamic, well-controlled and switchable particle patterns at the wall are due to an emerging diffusio-osmotic flow that takes its origin in the adjacent to the wall electrostatic diffuse layer, where the concentration gradients of surfactant are induced by light. The conventional nonporous particles are passive and can move only with already generated flow. However, porous colloids actively participate themselves in the flow generation mechanism at the wall, which also sets their interactions that can be very long ranged. This light-induced diffusio-osmosis opens novel avenues to manipulate colloidal particles and assemble them to various patterns. We show in particular how to create and split optically the confined regions of particles of tunable size and shape, where well-controlled flow-induced forces on the colloids could result in their crystalline packing, formation of dilute lattices of well-separated particles, and other states.}, language = {en} }