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  • PACS. 82.20.Mj Nonequilibrium kinetics - 05.70.Ln Nonequilibrium and irreversible thermodynamics  (2)
  • Turbulent Flows  (2)
  • Electrocardiography  (1)
  • Fluid Dynamics  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 16 (2000), S. 137-145 
    ISSN: 1434-6036
    Keywords: PACS. 82.20.Mj Nonequilibrium kinetics - 05.70.Ln Nonequilibrium and irreversible thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Fast self sustained waves of chemical or phase transformations, observed in several contexts in condensed matter effectively result in “gasless detonation". The phenomenon is modelled by coupling the reaction diffusion equation, describing chemical or phase transformations, and the wave equation, describing elastic perturbations. The coupling considered in this work involves (i) a dependence of the sound velocity on the chemical (phase) field, and (ii) the destruction of the initial chemical equilibrium when the strain exceeds a critical value (strain induced phase transition). Both the case of an initially unstable state (first order kinetics) and metastable state (second order kinetics) are considered. An exhaustive analytic and numerical study of travelling waves reveals the existence of supersonic modes of transformations. The practically important problem of ignition of fast waves by mechanical perturbation is investigated. With the present model, the critical strain necessary to ignite gasless detonation by local perturbations is determined.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 10 (1999), S. 379-383 
    ISSN: 1434-6036
    Keywords: PACS. 82.20.Mj Nonequilibrium kinetics - 05.70.Ln Nonequilibrium and irreversible thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Fast self sustained waves (autowaves) associated with chemical or phase transformations are observed in many situations in condensed matter. They are governed neither by diffusion of matter or heat (as in combustion processes) nor by a travelling shock wave (as in gaseous detonation). Instead, they result from a coupling between phase transformation and the stress field, and may be classified as gasless detonation autowaves in solids. We propose a simple model to describe these regimes. The model rests on the classical equations of elastic deformations in a 1-dimensional solid bar, with the extra assumption that the phase (chemical) transformation induces a change of the sound velocity. The transformations are assumed to occur through a chain branched mechanism, which starts when the mechanical stress exceeds a given threshold. Our investigation shows that supersonic autowaves exist in this model. In the absence of diffusion (dissipation factor, losses), a continuum of travelling wave solutions is found. In the presence of diffusion, a steady state supersonic wave solution is found, along with a slower wave controlled by diffusion.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2013-12-11
    Description: Author(s): Michel Voßkuhle, Emmanuel Lévêque, Michael Wilkinson, and Alain Pumir In turbulent suspensions, collision rates determine how rapidly particles coalesce or react with each other. To determine the collision rate, many numerical studies rely on the ghost collision approximation (GCA), which simply records how often pairs of point particles come within a threshold distan... [Phys. Rev. E 88, 063008] Published Tue Dec 10, 2013
    Keywords: Fluid Dynamics
    Print ISSN: 1539-3755
    Electronic ISSN: 1550-2376
    Topics: Physics
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  • 4
    Publication Date: 2011-07-15
    Description: Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves in a heterogeneous anatomical substrate. In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation. Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density rho(E) and a characteristic time, tau, for tissue depolarization that obeys the power law tau proportional, variant E(alpha). These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153959/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153959/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Luther, Stefan -- Fenton, Flavio H -- Kornreich, Bruce G -- Squires, Amgad -- Bittihn, Philip -- Hornung, Daniel -- Zabel, Markus -- Flanders, James -- Gladuli, Andrea -- Campoy, Luis -- Cherry, Elizabeth M -- Luther, Gisa -- Hasenfuss, Gerd -- Krinsky, Valentin I -- Pumir, Alain -- Gilmour, Robert F Jr -- Bodenschatz, Eberhard -- HL073644/HL/NHLBI NIH HHS/ -- HL075515/HL/NHLBI NIH HHS/ -- HL075515-S04/HL/NHLBI NIH HHS/ -- P41-EB001977/EB/NIBIB NIH HHS/ -- R01 HL073644/HL/NHLBI NIH HHS/ -- R01 HL073644-05/HL/NHLBI NIH HHS/ -- R01 HL075515/HL/NHLBI NIH HHS/ -- R01 HL075515-04/HL/NHLBI NIH HHS/ -- R01 HL075515-04S2/HL/NHLBI NIH HHS/ -- England -- Nature. 2011 Jul 13;475(7355):235-9. doi: 10.1038/nature10216.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Gottingen, Germany. stefan.luther@ds.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21753855" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atrial Fibrillation/*physiopathology ; Contrast Media ; Coronary Vessels/anatomy & histology ; Dogs ; Electric Countershock/instrumentation/*methods ; Electrocardiography ; Heart/anatomy & histology/*physiology/*physiopathology ; Ventricular Fibrillation/*physiopathology ; X-Ray Microtomography
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2018-01-12
    Description: Author(s): Jennifer Jucha, Aurore Naso, Emmanuel Lévêque, and Alain Pumir In cold clouds, small crystals of size ∼ 100 μ m settling in a turbulent fluid need to aggregate through collisions to form large hail or graupel particles. Using fully resolved direct numerical simulations, the role of the two main physical processes responsible for collisions is clarified, namely, turbulence and the difference in settling velocity due to different crystals orientations. [Phys. Rev. Fluids 3, 014604] Published Thu Jan 11, 2018
    Keywords: Turbulent Flows
    Electronic ISSN: 2469-990X
    Topics: Physics
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  • 6
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    American Physical Society (APS)
    Publication Date: 2017-07-18
    Description: Author(s): Alain Pumir Comparing systematically different turbulent flows with a mean shear, at similar Reynolds numbers, reveals a robust structure of the turbulent fluctuations, which does not depend much on the presence of walls. This fundamental property could help in devising parametrization of turbulent shear flows. [Phys. Rev. Fluids 2, 074602] Published Mon Jul 17, 2017
    Keywords: Turbulent Flows
    Electronic ISSN: 2469-990X
    Topics: Physics
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