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  • 1
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In kernlosen, wachsenden Zellfragmenten („Vorderstücke“) vonAcetabularia mediterranea undAcetabularia (Polyphysa) cliftonii vermehren sich die Chloroplasten. Die Zunahme innerhalb von 2–3 Wochen betrug bis zu maximal 132%. Im Gegensatz dazu bleibt in nichtwachsenden, kernlosen Teilstücken aus der Basalregion der Zelle („Hinterstücke“) die Chloroplastenzahl unverändert. Durch Verdunkelung in Gegenwart des Zellkernes (mit Rhizoid) läßt sich in „Hinterstücken“ die Potenz für Wachstum induzieren, die nach Entfernung des Rhizoids im Licht realisiert werden kann. Gleichzeitig erhalten die „Hinterstücke“ dabei die Fähigkeit zur Chloroplastenvermehrung. Wird in „Hinterstücken“ die Chloroplastenzahl herabgesetzt (auf etwa ein Viertel des Normalwertes), so wird dadurch ebenfalls eine Vermehrung der Chloroplasten ausgelöst. Die Versuche sprechen dafür, daß die Vermehrung der Chloroplasten offenbar vom Verhältnis Chloroplastenprotein/Cytoplasmaprotein abhängig ist und eine Störung dieser Relation durch Abzentrifugieren der Chloroplasten bei diesen Teilungen auslöst. Die Korrelation zwischen Wachstum und Chloroplastenvermehrung dürfte auf ähnliche Weise zu erklären sein.
    Notes: Summary Chloroplasts in growing enucleated cell fragments ofAcetabularia mediterranea andAcetabularia (Polyphysa) cliftonii multiply (obviously by division) and their number increases within 2–3 weeks up to 132%. However, there is no division of chloroplasts in non growing enucleated parts of the basal region of the cell. Capacity for growth can be induced in segments of the basal region which normally will not grow by dark treatment in presence of the nucleus. After removing the nucleus and transfering to light the enucleated parts grow and their number of chloroplasts increases. It is also possible to induce an increase of the number of chloroplasts by centrifugation of non growing enucleated cell fragments and thereby reducing the number of chloroplasts originally present. These results suggest that the increase in the number of chloroplasts very probably by division depends upon a certain ratio chloroplastic protein/cytoplasmic protein. Any disturbances of this ratio in favour of the cytoplasmic protein obviously leads to division of chloroplasts. It seems possible that the observed correlation between growth and the multiplication of chloroplast depends upon a similar mechanism.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-05-01
    Print ISSN: 1951-6355
    Electronic ISSN: 1951-6401
    Topics: Physics
    Published by Springer
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  • 3
    Publication Date: 2005-11-14
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
    Publication Date: 2019-11-01
    Print ISSN: 1054-1500
    Electronic ISSN: 1089-7682
    Topics: Physics
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  • 5
    Publication Date: 2017-03-17
    Electronic ISSN: 1367-2630
    Topics: Physics
    Published by Institute of Physics
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  • 6
    Publication Date: 2022-03-21
    Description: Time lags occur in a vast range of real-world dynamical systems due to finite reaction times or propagation speeds. Here we derive an analytical approach to determine the asymptotic stability of synchronous states in networks of coupled inertial oscillators with constant delay. Building on the master stability formalism, our technique provides necessary and sufficient delay master stability conditions. We apply it to two classes of potential future power grids, where processing delays in control dynamics will likely pose a challenge as renewable energies proliferate. Distinguishing between phase and frequency delay, our method offers an insight into how bifurcation points depend on the network topology of these system designs.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 7
    Publication Date: 2022-03-21
    Description: We show that the von Neumann–Lüders collapse rules in quantum mechanics always select the unique state that maximises the quantum relative entropy with respect to the premeasurement state, subject to the constraint that the postmeasurement state has to be compatible with the knowledge gained in the measurement. This way we provide an information theoretic characterisation of quantum collapse rules by means of the maximum relative entropy principle.
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  • 8
    Publication Date: 2022-03-21
    Description: The ongoing transition to renewable energy supply comes with a restructuring of power grids, changing their effective interaction topologies, more and more strongly decentralizing them and substantially modifying their input, output, and response characteristics. All of these changes imply that power grids become increasingly affected by collective, nonlinear dynamic phenomena, structurally and dynamically more distributed and less predictable in space and time, more heterogeneous in its building blocks, and as a consequence less centrally controllable. Here cornerstone aspects of data-driven and mathematical modeling of collective dynamical phenomena emerging in real and model power grid networks by combining theories from nonlinear dynamics, stochastic processes and statistical physics, anomalous statistics, optimization, and graph theory are reviewed. The mathematical background required for adequate modeling and analysis approaches is introduced, an overview of power system models is given, and a range of collective dynamical phenomena are focused on, including synchronization and phase locking, flow (re)routing, Braess’s paradox, geometric frustration, and spreading and localization of perturbations and cascading failures, as well as the nonequilibrium dynamics of power grids, where fluctuations play a pivotal role.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 9
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    In:  New Journal of Physics
    Publication Date: 2022-03-21
    Description: Many high-dimensional complex systems exhibit an enormously complex landscape of possible asymptotic states. Here, we present a numerical approach geared towards analyzing such systems. It is situated between the classical analysis with macroscopic order parameters and a more thorough, detailed bifurcation analysis. With our machine learning method, based on random sampling and clustering methods, we are able to characterize the different asymptotic states or classes thereof and even their basins of attraction. In order to do this, suitable, easy to compute, statistics of trajectories with randomly generated initial conditions and parameters are clustered by an algorithm such as DBSCAN. Due to its modular and flexible nature, our method has a wide range of possible applications in many disciplines. While typical applications are oscillator networks, it is not limited only to ordinary differential equation systems, every complex system yielding trajectories, such as maps or agent-based models, can be analyzed, as we show by applying it the Dodds–Watts model, a generalized SIRS-model, modeling social and biological contagion. A second order Kuramoto model, used, e.g. to investigate power grid dynamics, and a Stuart–Landau oscillator network, each exhibiting a complex multistable regime, are shown as well. The method is available to use as a package for the Julia language.
    Type: info:eu-repo/semantics/article
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  • 10
    Publication Date: 2022-03-21
    Description: Coupled oscillator networks show complex interrelations between topological characteristics of the network and the nonlinear stability of single nodes with respect to large but realistic perturbations. We extend previous results on these relations by incorporating sampling-based measures of the transient behaviour of the system, its survivability, as well as its asymptotic behaviour, its basin stability. By combining basin stability and survivability we uncover novel, previously unknown asymptotic states with solitary, desynchronized oscillators which are rotating with a frequency different from their natural one. They occur almost exclusively after perturbations at nodes with specific topological properties. More generally we confirm and significantly refine the results on the distinguished role tree-shaped appendices play for nonlinear stability. We find a topological classification scheme for nodes located in such appendices, that exactly separates them according to their stability properties, thus establishing a strong link between topology and dynamics. Hence, the results can be used for the identification of vulnerable nodes in power grids or other coupled oscillator networks. From this classification we can derive general design principles for resilient power grids. We find that striving for homogeneous network topologies facilitates a better performance in terms of nonlinear dynamical network stability. While the employed second-order Kuramoto-like model is parametrised to be representative for power grids, we expect these insights to transfer to other critical infrastructure systems or complex network dynamics appearing in various other fields.
    Type: info:eu-repo/semantics/article
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