Physik - Open Access LMU - Teil 01/02

Ludwig-Maximilians-Universität München
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Physik - Open Access LMU - Teil 01/02 Podcast

Die Universitätsbibliothek (UB) verfügt über ein umfangreiches Archiv an elektronischen Medien, das von Volltextsammlungen über Zeitungsarchive, Wörterbücher und Enzyklopädien bis hin zu ausführlichen Bibliographien und mehr als 1000 Datenbanken reicht. Auf iTunes U stellt die UB unter anderem eine Auswahl an elektronischen Publikationen der Wissenschaftlerinnen und Wissenschaftler an der LMU bereit. (Dies ist der 1. von 2 Teilen der Sammlung 'Physik - Open Access LMU'.)

  1. 01/01/2013

    Cavity-enhanced optical detection of carbon nanotube Brownian motion

    Physik - Open Access LMU - Teil 01/02

  2. 01/01/2013

    Klärung des Informationsbegriffs

    Eine naturphilosophische Leitwährung für die Beschreibung der Wirlichkeit ist bereits bei Aristoteles die Form. Sie informiert die Materie und vermittelt dadurch das Sein. Der Informationsbegriff jedoch ist multivalent: man kann zwischen potentieller Information (QuBits), basaler einfacher Information (Bits) und komplexer Information (Systemordner-Information) unterscheiden. Die komplexe Information wird im Bit kodiert, indem es das QuBit disponiert. Die Kodierung erfolgt holografisch und somit analog. Letztlich inkarnieren sich Systeme in der physikalischen Wirklichkeit, indem sie sie komplex informieren (ordnen, ermöglichen, steuern, formieren). Das Universum würde dann der Materialisierung und Dekodierung von autopoetischen Systemen dienen.

  3. 01/01/2013

    Role of particle conservation in self-propelled particle systems

    Actively propelled particles undergoing dissipative collisions are known to develop a state of spatially distributed coherently moving clusters. For densities larger than a characteristic value, clusters grow in time and form a stationary well-ordered state of coherent macroscopic motion. In this work we address two questions. (i) What is the role of the particles’ aspect ratio in the context of cluster formation, and does the particle shape affect the system’s behavior on hydrodynamic scales? (ii) To what extent does particle conservation influence pattern formation? To answer these questions we suggest a simple kinetic model permitting us to depict some of the interaction properties between freely moving particles and particles integrated in clusters. To this end, we introduce two particle species: single and cluster particles. Specifically, we account for coalescence of clusters from single particles, assembly of single particles on existing clusters, collisions between clusters and cluster disassembly. Coarse graining our kinetic model, (i) we demonstrate that particle shape (i.e. aspect ratio) shifts the scale of the transition density, but does not impact the instabilities at the ordering threshold and (ii) we show that the validity of particle conservation determines the existence of a longitudinal instability, which tends to amplify density heterogeneities locally, and in turn triggers a wave pattern with wave vectors parallel to the axis of macroscopic order. If the system is in contact with a particle reservoir, this instability vanishes due to a compensation of density heterogeneities.

  4. 01/01/2013

    Stability of Localized Wave Fronts in Bistable Systems

    Localized wave fronts are a fundamental feature of biological systems from cell biology to ecology. Here, we study a broad class of bistable models subject to self-activation, degradation, and spatially inhomogeneous activating agents. We determine the conditions under which wave-front localization is possible and analyze the stability thereof with respect to extrinsic perturbations and internal noise. It is found that stability is enhanced upon regulating a positional signal and, surprisingly, also for a low degree of binding cooperativity. We further show a contrasting impact of self-activation to the stability of these two sources of destabilization. DOI: 10.1103/PhysRevLett.110.038102

  5. 29/12/2012

    Few electron double quantum dot in an isotopically purified 28Si quantum well

    Physik - Open Access LMU - Teil 01/02

  6. 07/11/2012

    Increasing organic solar cell efficiency with polymer interlayers

    We demonstrate how organic solar cell efficiency can be increased by introducing a pure polymer interlayer between the PEDOT:PSS layer and the polymer: fullerene blend. We observe an increase in device efficiency with three different material systems over a number of devices. Using both electrical characterization and numerical modeling we show that the increase in efficiency is caused by optical absorption in the pure polymer layer and hence efficient charge separation at the polymer bulkheterojunction interface.

  7. 01/09/2012

    Nucleation-induced transition to collective motion in active systems

    While the existence of polar ordered states in active systems is well established, the dynamics of the self-assembly processes are still elusive. We study a lattice gas model of self-propelled elongated particles interacting through excluded volume and alignment interactions, which shows a phase transition from an isotropic to a polar ordered state. By analyzing the ordering process we find that the transition is driven by the formation of a critical nucleation cluster and a subsequent coarsening process. Moreover, the time to establish a polar ordered state shows a power-law divergence.

  8. 01/06/2012

    Microtubule Length Regulation by Molecular Motors

    Length regulation of microtubules (MTs) is essential for many cellular processes. Molecular motors like kinesin-8, which move along MTs and also act as depolymerases, are known as key players in MT dynamics. However, the regulatory mechanisms of length control remain elusive. Here, we investigate a stochastic model accounting for the interplay between polymerization kinetics and motor-induced depolymerization. We determine the dependence of MT length and variance on rate constants and motor concentration. Moreover, our analyses reveal how collective phenomena lead to a well-defined MT length.

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About

Die Universitätsbibliothek (UB) verfügt über ein umfangreiches Archiv an elektronischen Medien, das von Volltextsammlungen über Zeitungsarchive, Wörterbücher und Enzyklopädien bis hin zu ausführlichen Bibliographien und mehr als 1000 Datenbanken reicht. Auf iTunes U stellt die UB unter anderem eine Auswahl an elektronischen Publikationen der Wissenschaftlerinnen und Wissenschaftler an der LMU bereit. (Dies ist der 1. von 2 Teilen der Sammlung 'Physik - Open Access LMU'.)

Information

  • Creator
    Ludwig-Maximilians-Universität München
  • Years Active
    2011 - 2013
  • Episodes
    250
  • Rating
    Clean
  • Copyright
    © Ludwig-Maximilians-Universität München
  • Show Website
    Physik - Open Access LMU - Teil 01/02

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