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Blackburn E. Characterizing self-assembled structures made with magnetic Janus nanoparticles. IUCrJ 2024; 11:131-132. [PMID: 38427456 PMCID: PMC10916292 DOI: 10.1107/s2052252524001532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/03/2024]
Abstract
Small-angle X-ray scattering has revealed how magnetic Janus particles pair up in solutions in small and large magnetic fields.
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Affiliation(s)
- Elizabeth Blackburn
- Division of Synchrotron Radiation Research, Department of Physics, Lund University, SE-22100 Lund, Sweden
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2
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Hu Y, Liu C, Shen H, Xiao G, Li J. A Unified Gas-Kinetic Particle Method for Radiation Transport in an Anisotropic Scattering Medium. Entropy (Basel) 2024; 26:52. [PMID: 38248178 DOI: 10.3390/e26010052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 12/15/2023] [Accepted: 12/30/2023] [Indexed: 01/23/2024]
Abstract
In this paper, a unified gas kinetic particle (UGKP) method is developed for radiative transfer in both absorbing and anisotropic scattering media. This numerical method is constructed based on our theoretical work on the model reduction for an anisotropic scattering system. The macroscopic solver of this method directly solves the macroscopic anisotropic diffusion equations, eliminating the need to solve higher-order moment equations. The reconstruction of macroscopic scattering source in the microscopic solver, based on the multiscale equivalent phase function we proposed in this work, has also been simplified as one single scattering process, significantly reducing the computational costs. The proposed method has also the property of asymptotic preserving. In the optically thick regime, the proposed method solves the diffusion limit equations for an anisotropic system. In the optically thin regime, the kinetic processes of photon transport are simulated. The consistency and efficiency of the proposed method have been validated by numerical tests in a wide range of flow regimes. The novel equivalent scattering source reconstruction can be used for various transport processes, and the proposed numerical scheme is widely applicable in high-energy density engineering applications.
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Affiliation(s)
- Yuan Hu
- Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
| | - Chang Liu
- Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
| | - Huayun Shen
- Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
| | - Gang Xiao
- Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
| | - Jinghong Li
- Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
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Manna G, Zinn T, Sharpnack L, Narayanan T. Orientational ordering and assembly of silica-nickel Janus particles in a magnetic field. IUCrJ 2024; 11:109-119. [PMID: 38099813 PMCID: PMC10833383 DOI: 10.1107/s205225252301000x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 11/16/2023] [Indexed: 01/10/2024]
Abstract
The orientation ordering and assembly behavior of silica-nickel Janus particles in a static external magnetic field were probed by ultra small-angle X-ray scattering (USAXS). Even in a weak applied field, the net magnetic moments of the individual particles aligned in the direction of the field, as indicated by the anisotropy in the recorded USAXS patterns. X-ray photon correlation spectroscopy (XPCS) measurements on these suspensions revealed that the corresponding particle dynamics are primarily Brownian diffusion [Zinn, Sharpnack & Narayanan (2023). Soft Matter, 19, 2311-2318]. At higher fields, the magnetic forces led to chain-like configurations of particles, as indicated by an additional feature in the USAXS pattern. A theoretical framework is provided for the quantitative interpretation of the observed anisotropic scattering diagrams and the corresponding degree of orientation. No anisotropy was detected when the magnetic field was applied along the beam direction, which is also replicated by the model. The method presented here could be useful for the interpretation of oriented scattering patterns from a wide variety of particulate systems. The combination of USAXS and XPCS is a powerful approach for investigating asymmetric colloidal particles in external fields.
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Affiliation(s)
| | - Thomas Zinn
- ESRF – The European Synchrotron, 38043 Grenoble, France
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Chen H, Baitenov A, Li Y, Vasileva E, Popov S, Sychugov I, Yan M, Berglund L. Thickness Dependence of Optical Transmittance of Transparent Wood: Chemical Modification Effects. ACS Appl Mater Interfaces 2019; 11:35451-35457. [PMID: 31483595 PMCID: PMC6776381 DOI: 10.1021/acsami.9b11816] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 09/04/2019] [Indexed: 05/21/2023]
Abstract
Transparent wood (TW) is an emerging optical material combining high optical transmittance and haze for structural applications. Unlike nonscattering absorbing media, the thickness dependence of light transmittance for TW is complicated because optical losses are also related to increased photon path length from multiple scattering. In the present study, starting from photon diffusion equation, it is found that the angle-integrated total light transmittance of TW has an exponentially decaying dependence on sample thickness. The expression reveals an attenuation coefficient which depends not only on the absorption coefficient but also on the diffusion coefficient. The total transmittance and thickness were measured for a range of TW samples, from both acetylated and nonacetylated balsa wood templates, and were fitted according to the derived relationship. The fitting gives a lower attenuation coefficient for the acetylated TW compared to the nonacetylated one. The lower attenuation coefficient for the acetylated TW is attributed to its lower scattering coefficient or correspondingly lower haze. The attenuation constant resulted from our model hence can serve as a singular material parameter that facilitates cross-comparison of different sample types, at even different thicknesses, when total optical transmittance is concerned. The model was verified with two other TWs (ash and birch) and is in general applicable to other scattering media.
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Affiliation(s)
- Hui Chen
- Wallenberg Wood
Science Center, Department of Fiber and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, Stockholm 100 44, Sweden
| | - Adil Baitenov
- Department of Applied Physics, School of Engineering
Sciences, KTH Royal Institute of Technology, Isafjordsgatan 22, Kista 164 40, Sweden
| | - Yuanyuan Li
- Wallenberg Wood
Science Center, Department of Fiber and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, Stockholm 100 44, Sweden
| | - Elena Vasileva
- Department of Applied Physics, School of Engineering
Sciences, KTH Royal Institute of Technology, Isafjordsgatan 22, Kista 164 40, Sweden
| | - Sergei Popov
- Department of Applied Physics, School of Engineering
Sciences, KTH Royal Institute of Technology, Isafjordsgatan 22, Kista 164 40, Sweden
| | - Ilya Sychugov
- Department of Applied Physics, School of Engineering
Sciences, KTH Royal Institute of Technology, Isafjordsgatan 22, Kista 164 40, Sweden
- (I.S.)
| | - Max Yan
- Department of Applied Physics, School of Engineering
Sciences, KTH Royal Institute of Technology, Isafjordsgatan 22, Kista 164 40, Sweden
- (M.Y.)
| | - Lars Berglund
- Wallenberg Wood
Science Center, Department of Fiber and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, Stockholm 100 44, Sweden
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Biasin E, van Driel TB, Levi G, Laursen MG, Dohn AO, Moltke A, Vester P, Hansen FBK, Kjaer KS, Harlang T, Hartsock R, Christensen M, Gaffney KJ, Henriksen NE, Møller KB, Haldrup K, Nielsen MM. Anisotropy enhanced X-ray scattering from solvated transition metal complexes. J Synchrotron Radiat 2018; 25:306-315. [PMID: 29488907 DOI: 10.1107/s1600577517016964] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/24/2017] [Indexed: 05/23/2023]
Abstract
Time-resolved X-ray scattering patterns from photoexcited molecules in solution are in many cases anisotropic at the ultrafast time scales accessible at X-ray free-electron lasers (XFELs). This anisotropy arises from the interaction of a linearly polarized UV-Vis pump laser pulse with the sample, which induces anisotropic structural changes that can be captured by femtosecond X-ray pulses. In this work, a method for quantitative analysis of the anisotropic scattering signal arising from an ensemble of molecules is described, and it is demonstrated how its use can enhance the structural sensitivity of the time-resolved X-ray scattering experiment. This method is applied on time-resolved X-ray scattering patterns measured upon photoexcitation of a solvated di-platinum complex at an XFEL, and the key parameters involved are explored. It is shown that a combined analysis of the anisotropic and isotropic difference scattering signals in this experiment allows a more precise determination of the main photoinduced structural change in the solute, i.e. the change in Pt-Pt bond length, and yields more information on the excitation channels than the analysis of the isotropic scattering only. Finally, it is discussed how the anisotropic transient response of the solvent can enable the determination of key experimental parameters such as the instrument response function.
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Affiliation(s)
- Elisa Biasin
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Tim B van Driel
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Gianluca Levi
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Mads G Laursen
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Asmus O Dohn
- Faculty of Physical Sciences, University of Iceland, Reykjavik, Iceland
| | - Asbjørn Moltke
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Peter Vester
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Frederik B K Hansen
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Kasper S Kjaer
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Tobias Harlang
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Robert Hartsock
- PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Morten Christensen
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Kelly J Gaffney
- PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Niels E Henriksen
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Klaus B Møller
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Kristoffer Haldrup
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
| | - Martin M Nielsen
- Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
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Dufouleur J, Veyrat L, Dassonneville B, Nowka C, Hampel S, Leksin P, Eichler B, Schmidt OG, Büchner B, Giraud R. Enhanced Mobility of Spin-Helical Dirac Fermions in Disordered 3D Topological Insulators. Nano Lett 2016; 16:6733-6737. [PMID: 27706936 DOI: 10.1021/acs.nanolett.6b02060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The transport length ltr and the mean free path le are determined for bulk and surface states in a Bi2Se3 nanoribbon by quantum transport and transconductance measurements. We show that the anisotropic scattering of spin-helical Dirac fermions results in a strong enhancement of ltr (≈ 200 nm) and of the related mobility μtr (≈ 4000 cm2 V-1 s-1), which confirms theoretical predictions.1 Despite strong disorder, the long-range nature of the scattering potential gives a large ratio ltr/le ≈ 8, likely limited by bulk/surface coupling. This suggests that the spin-flip length lsf ≈ ltr could reach the micron size in materials with a reduced bulk doping and paves the way for building functionalized spintronic and ballistic electronic devices out of disordered 3D topological insulators.
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Affiliation(s)
| | - Louis Veyrat
- IFW Dresden , P.O. Box 270116, D-01171 Dresden, Germany
| | | | | | - Silke Hampel
- IFW Dresden , P.O. Box 270116, D-01171 Dresden, Germany
| | - Pavel Leksin
- IFW Dresden , P.O. Box 270116, D-01171 Dresden, Germany
| | | | | | - Bernd Büchner
- IFW Dresden , P.O. Box 270116, D-01171 Dresden, Germany
| | - Romain Giraud
- IFW Dresden , P.O. Box 270116, D-01171 Dresden, Germany
- INAC-SPINTEC, Univ. Grenoble Alpes/CNRS/CEA , 17 Avenue des Martyrs, 38054 Grenoble, France
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Bayer FL, Hu S, Maier A, Weber T, Anton G, Michel T, Riess CP. Reconstruction of scalar and vectorial components in X-ray dark-field tomography. Proc Natl Acad Sci U S A 2014; 111:12699-704. [PMID: 25136091 DOI: 10.1073/pnas.1321080111] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Grating-based X-ray dark-field imaging is a novel technique for obtaining image contrast for object structures at size scales below setup resolution. Such an approach appears particularly beneficial for medical imaging and nondestructive testing. It has already been shown that the dark-field signal depends on the direction of observation. However, up to now, algorithms for fully recovering the orientation dependence in a tomographic volume are still unexplored. In this publication, we propose a reconstruction method for grating-based X-ray dark-field tomography, which models the orientation-dependent signal as an additional observable from a standard tomographic scan. In detail, we extend the tomographic volume to a tensorial set of voxel data, containing the local orientation and contributions to dark-field scattering. In our experiments, we present the first results of several test specimens exhibiting a heterogeneous composition in microstructure, which demonstrates the diagnostic potential of the method.
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