Universität Stuttgart

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Institute: search.filters.UBSInstitut.Institut für Theoretische Physik IIInstitute: search.filters.UBSInstitut.Fakultätsübergreifend / Sonstige EinrichtungSubject: search.filters.subject.530Publication Type: search.filters.UBSTyp.ZeitschriftenartikelStart date: 2015End date: 2015

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Now showing 1 - 3 of 3
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    Thermodynamics of micro- and nano-systems driven by periodic temperature variations
    (2015) Brandner, Kay; Saito, Keiji; Seifert, Udo
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    Functional integral approach to time-dependent heat exchange in open quantum systems : general method and applications
    (2015) Carrega, M.; Solinas, P.; Braggio, A.; Sassetti, M.; Weiß, Ulrich
    We establish the path integral approach for the time-dependent heat exchange of an externally driven quantum system coupled to a thermal reservoir. We derive the relevant influence functional and present an exact formal expression for the moment generating functional which carries all statistical properties of the heat exchange process for general linear dissipation. The method is applied to the time-dependent average heat transfer in the dissipative two-state system (TSS). We show that the heat can be written as a convolution integral which involves the population and coherence correlation functions of the TSS and additional correlations due to a polarization of the reservoir. The corresponding expression can be solved in the weak-damping limit both for white noise and for quantum mechanical coloured noise. The implications of pure quantum effects are discussed. Altogether a complete description of the dynamics of the average heat transfer ranging from the classical regime down to zero temperature is achieved.
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    Multiscale approaches to protein-mediated interactions between membranes : relating microscopic and macroscopic dynamics in radially growing adhesions
    (2015) Bihr, Timo; Seifert, Udo; Smith, Ana-Sunčana
    Macromolecular complexation leading to coupling of two or more cellular membranes is a crucial step in a number of biological functions of the cell. While other mechanisms may also play a role, adhesion always involves the fluctuations of deformable membranes, the diffusion of proteins and the molecular binding and unbinding. Because these stochastic processes couple over a multitude of time and length scales, theoretical modeling of membrane adhesion has been a major challenge. Here we present an effective Monte Carlo scheme within which the effects of the membrane are integrated into local rates for molecular recognition. The latter step in the Monte Carlo approach enables us to simulate the nucleation and growth of adhesion domains within a system of the size of a cell for tens of seconds without loss of accuracy, as shown by comparison to 106 times more expensive Langevin simulations. To perform this validation, the Langevin approach was augmented to simulate diffusion of proteins explicitly, together with reaction kinetics and membrane dynamics. We use the Monte Carlo scheme to gain deeper insight to the experimentally observed radial growth of micron sized adhesion domains, and connect the effective rate with which the domain is growing to the underlying microscopic events. We thus demonstrate that our technique yields detailed information about protein transport and complexation in membranes, which is a fundamental step toward understanding even more complex membrane interactions in the cellular context.