| 1. |
- Bergstrand, Sten, et al.
(author)
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Activities of the IERS Working Group on Site Survey and Co-location
- 2016
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In: International VLBI Service for Geodesy and Astrometry 2016 General Meeting Proceedings. - Greenbelt, MD : National Aeronautics and Space Administration. ; , s. 113-117
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Conference paper (other academic/artistic)abstract
- The objective of the International Earth Rotation and Reference Systems Service (IERS) Working Group on Site Survey and Co-location is to improve local measurements at space geodesy sites. We appointed dedicated Points of Contact (POC) with the four different services of IERS as well as the NASA Space Geodesy Project in order to improve the efficiency of internal communication within the working group. Following the REFAG2014 conference, the POCs agreed on a common and general terminology on local ties that clarifies the communication regarding site surveying and co-location issues between and within the IERS services. We give brief introductions to the different observation techniques and mention some contemporary issues related to site surveying and co-location.
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| 2. |
- Brant, William R., et al.
(author)
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Local structure transformations promoting high lithium diffusion in defect perovskite type structures
- 2023
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In: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 441
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Journal article (peer-reviewed)abstract
- Defect perovskites, AxBO3 such as (Li3xLa2/3-x)TiO3, are attracting attention as high capacity electrodes in lithium-ion batteries. However, the mechanism enabling high lithium storage capacities has not been fully investigated. In this work, the reversible insertion and removal of lithium up to an average A-site cavity occupancy of 1.71 in the defect perovskite (Li0.18Sr0.66)(Ti0.5Nb0.5)O3 is investigated. It was shown that subtle lithium reorganization during lithiation has a significant impact on enabling high capacity. Contrary to previous studies, lithium was coordinated to triangular faces of Ti/Nb oxygen octahedra and offset from O4 windows between A-site cavities in the as-synthesised material. Upon electrochemical lithiation Li-Li repulsion redistributes of all the lithium towards the O4 window position resulting in a loss of lithium mobility. Surprisingly, the mobility is regained during over-lithiation and following multiple electrochemical cycles. It is suggested that lithium reorganisation into the center of the O4 window alleviates the Li-Li repulsion and modifies the diffusion behavior from site percolation to bond percolation. The results obtained provide valuable insight into the chemical drivers enabling higher capacities and enhanced diffusion in defect perovskites. More broadly the study delivers fundamental understanding on the non-equilibrium structural transformations occurring within electrode materials during repeated electrochemical cycles.
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| 3. |
- Klopotek, Grzegorz, 1990, et al.
(author)
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Results from the VLBI Analysis Software Comparison Campaign 2015
- 2016
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In: IVS 2016 General Meeting Proceedings "New Horizons with VGOS". Edited by Dirk Behrend, Karen D. Baver, and Kyla L. Armstrong, NASA/CP-2016-219016. ; , s. 203-207
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Conference paper (other academic/artistic)abstract
- The aim of the VLBI Analysis Software Comparison Campaign 2015 (VASCC2015) was to compare differentVLBI analysis software packages on the basis of computed theoretical delays. Eleven research groups and institutes participated in this project which allowed us to compare software packages that are used in operational VLBI analyses or that are still under development. We present the first results and we show how well the individual software packages agree at this stage.
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| 4. |
- Lundgren, Edvin, et al.
(author)
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Geometry of the valence transition induced surface reconstruction of Sm(0001).
- 2002
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 88:13, s. 136102-136102
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Journal article (peer-reviewed)abstract
- We present a structural determination of the surface reconstruction of the Sm(0001) surface using surface x-ray diffraction, scanning tunneling microscopy, and ab initio calculations. The reconstruction is associated with a large (22%) expansion of the atomic radius for the top monolayer surface Sm atoms. The mechanism driving the surface reconstruction in Sm is unique among all elements and is connected to the strong correlations of the 4f electrons in Sm and the intermediate valence observed in certain Sm compounds. The atoms constituting the top monolayer of Sm(0001) have vastly different chemical properties compared to the layer underneath and behave as if they were an adsorbate of a different chemical species.
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| 5. |
- Meinhardt, Sebastian, et al.
(author)
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Separation of Chiral Particles in Micro- or Nanofluidic Channels
- 2012
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:21, s. 214504-
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Journal article (peer-reviewed)abstract
- We propose a method to separate enantiomers in microfluidic or nanofluidic channels. It requires flow profiles that break chiral symmetry and have regions with high local shear. Such profiles can be generated in channels confined by walls with different hydrodynamic boundary conditions (e.g., slip lengths). Because of a nonlinear hydrodynamic effect, particles with different chirality migrate at different speeds and can be separated. The mechanism is demonstrated by computer simulations. We investigate the influence of thermal fluctuations (i.e., the Peclet number) and show that the effect disappears in the linear response regime. The details of the microscopic flow are important and determine which volume forces are necessary to achieve separation.
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| 6. |
- Wölfer, Ralf, et al.
(author)
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Developmental Dynamics of Intergroup Contact and Intergroup Attitudes : Long-Term Effects in Adolescence and Early Adulthood
- 2016
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In: Child Development. - : Wiley-Blackwell. - 0009-3920 .- 1467-8624. ; 87:5, s. 1466-1478
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Journal article (peer-reviewed)abstract
- Intergroup contact represents a powerful way to improve intergroup attitudes and to overcome prejudice and discrimination. However, long-term effects of intergroup contact that consider social network dynamics have rarely been studied at a young age. Study 1 validated an optimized social network approach to investigate intergroup contact (N=6,457; M-age=14.91years). Study 2 explored the developmental trajectories of intergroup contact by applying this validated network approach in a cross-sequential design (four-cohort-four-wave; N=3,815; 13-26years). Accelerated growth curve models showed that contact predicts the development of attitudes in adolescence, whereas acquired attitudes buffer against decreasing contact in adulthood. Findings highlight the potential of social network analysis and the developmental importance of early intergroup contact experiences.
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