Universität Stuttgart

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Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.Max-Planck-Institut für Intelligente SystemeStart date: 2019End date: 2019

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Now showing 1 - 4 of 4
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    Novel X-ray lenses for direct and coherent imaging
    (2019) Sanli, Umut Tunca; Schütz, Gisela (Prof. Dr.)
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    Interfaces in fluids of ionic liquid crystals
    (2019) Bartsch, Hendrik; Dietrich, Siegfried (Prof. Dr.)
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    High-density hydrogen monolayer formation and isotope diffusion in porous media
    (2019) Balderas-Xicohténcatl, Rafael; Schütz, Gisela (Prof. Dr.)
    This thesis is focused on two fundamental aspects of hydrogen physisorption. First, the density of a single layer of adsorbed hydrogen molecules is studied at temperatures close the boiling point (20 K). These systematic experiments give an explanation to high H2 monolayer capacity as a high-density phase of adsorbed hydrogen. Secondly, the diffusion of the hydrogen molecules through a porous material (ZIF-8) is studied using a commercially available adsorption apparatus. Establishing that gas adsorption experiments can be used to study hydrogen diffusion and isotope separation at temperatures close the boiling point.
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    Correlations and forces in sheared fluids with or without quenching
    (2019) Rohwer, Christian M.; Maciołek, Anna; Dietrich, Siegfried; Krüger, Matthias
    Spatial correlations play an important role in characterizing material properties related to non-local effects. Inter alia, they can give rise to fluctuation-induced forces. Equilibrium correlations in fluids provide an extensively studied paradigmatic case, in which their range is typically bounded by the correlation length. Out of equilibrium, conservation laws have been found to extend correlations beyond this length, leading, instead, to algebraic decays. In this context, here we present a systematic study of the correlations and forces in fluids driven out of equilibrium simultaneously by quenching and shearing, both for non-conserved as well as for conserved Langevin-type dynamics. We identify which aspects of the correlations are due to shear, due to quenching, and due to simultaneously applying both, and how these properties depend on the correlation length of the system and its compressibility. Both shearing and quenching lead to long-ranged correlations, which, however, differ in their nature as well as in their prefactors, and which are mixed up by applying both perturbations. These correlations are employed to compute non-equilibrium fluctuation-induced forces in the presence of shear, with or without quenching, thereby generalizing the framework set out by Dean and Gopinathan. These forces can be stronger or weaker compared to their counterparts in unsheared systems. In general, they do not point along the axis connecting the centers of the small inclusions considered to be embedded in the fluctuating medium. Since quenches or shearing appear to be realizable in a variety of systems with conserved particle number, including active matter, we expect these findings to be relevant for experimental investigations.