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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 3967-3979 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We apply a statistical–thermodynamic approach to the study of a particular physical system (two sets of nonlinearly coupled oscillators), driven far away from equilibrium. Such a system displays a kind of complex behavior consisting in the so-called Fröhlich effect leading in steady-state conditions to a nonequilibrium phase condensation resembling the Bose–Einstein condensation of systems in equilibrium. A kind of "two-fluid model" arises: the "normal nonequilibrium phase" and Fröhlich condensate or "nonequilibrium superphase," which is shown to be an attractor of the system. We work out some aspects of the irreversible thermodynamics of this dissipative complex system. Particular nonlinear properties are discussed and Lyapunov exponents determined. This kind of system gives a good modeling of polar vibration modes in polymers and biopolymers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2692-2700 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the framework of a nonequilibrium statistical ensemble formalism, consisting of the so-called Nonequilibrium Statistical Operator Method, we discuss the question of the choice of the space of thermohydrodynamic states. We consider in particular the relevant question of the truncation of description (reduction of the dimension of the state space). A criterion for justifying the different levels of truncation is derived. It depends on the range of wavelengths and frequencies which are the relevant ones for the characterization, in terms of normal modes, of the thermohydrodynamic motion in a nonequilibrium open system. Applications to the cases of thermal-sensitive resins and of n-doped polar semiconductors are done, numerical results are presented, and experimental observation is discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 7580-7586 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: On the basis of the generalized Mori–Heisenberg–Langevin equations presented in the preceding paper, we derive and analyze the informational-statistical thermodynamic properties of a fluid of bosons away from equilibrium. We derive the informational entropy and its production, proceeding to an analysis of the several contributions to these state functions arising out of the evolution of dissipative processes in the system. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 7568-7579 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Within the scope of a nonequilibrium statistical ensemble formalism we derive a hierarchy of equations of evolution for a set of basic thermo-hydrodynamic variables, which describe the macroscopic nonequilibrium state of a fluid of bosons. This set is composed of the energy density and number density and their fluxes of all order. The resulting equations can be considered as far-reaching generalizations of those in Mori's approach. They involve nonlocality in space and retro-effects (i.e. correlations in space and time respectively), are highly nonlinear, and account for irreversible behavior in the macroscopic evolution of the system. The different contributions to these kinetic equations are analyzed and the Markovian limit is obtained. In the follow up article we consider the nonequilibrium thermodynamic properties that the formalism provides. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2099-2110 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the domain of Statistical Mechanics of nonequilibrium-nonlinear (dissipative) systems based on a generalized Gibbs–Boltzmann ensemble formalism, it may be highlighted the so-called Nonequilibrium Statistical Operator Method, and, particularly, Zubarev's approach. We report here a detailed analysis of a case consisting in a generalized nonequilibrium grand-canonical ensemble. Its construction requires to introduce besides the traditional densities of energy and the particle number their nonconserving-dissipative fluxes of all order. The description is quite appropriate to provide a framework for the construction of a nonclassical thermo-hydrodynamics, which is briefly described. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 7383-7396 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider the question of the definition of thermodynamic-like variables in the context of a statistical thermodynamics, which is a large generalization of Gibbs statistical thermostatics and linear and local-equilibrium classical irreversible thermodynamics. It is based on a nonequilibrium ensemble approach known as the nonequilibrium statistical operator method. Some of these quasithermodynamic variables are characteristic of the nonequilibrium state and go to zero in the limit of local or global equilibrium, but others go over the thermodynamic variables that are present in such a limit. We consider in particular temperature-like variables for the different subsystems of the sample. For illustration we apply the theory to the study of optical properties of highly photoexcited plasma in semiconductors, following a good agreement between theory and experimental data. It is shown that high-resolution spectroscopy provides an excellent experimental testing ground for corroboration of the theoretical concepts, and a quite appropriate way for characterizing and measuring nonequilibrium thermodynamic-like variables. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 23 (1980), S. 539-559 
    ISSN: 1572-9613
    Keywords: Response function ; nonequilibrium thermodynamic Green's functions ; nonequilibrium statistical operator ; generalized Langevin equations ; photoexcited semiconductor plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A formalism to determine the response function of a sample in conditions far from thermal equilibrium is presented. It consists in a generalization of scattering theory coupled to the statistical theory of irreversible processes, the nonequilibrium statistical operator method, developed by Zubarev. The scattering cross section is expressed in terms of double-time correlation functions, which are related to appropriate nonequilibrium thermodynamic Green's functions. The latter are also used to treat generalized transport equations, and, as an illustration, the method is applied to the study of the time-resolved Raman spectroscopy of a photoexcited semiconductor plasma.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 689-697 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We consider the question of long-range propagation of informational signals in biosystems. This is done for the case of a modeled biosystem of the type considered by H. Fröhlich and A. S. Davydov but under general nonequilibrium thermodynamic conditions. For that purpose we resort to the so-called informational statistical thermodynamics. It is shown that Fröhlich's effect may follow in this system. It consists in the emergence of a self-organized dissipative homogeneous and stationary structure (in Prigogine's sense), resembling a nonequilibrium Bose-Einstein condensation in the low-lying-in-frequency modes of polar vibrations. It follows once a critical level of pumping of metabolic energy is achieved. Furthermore, it is shown that signals in this system propagate in the form of Davydov solitons, which are strongly thermally damped in near equilibrium at physiological conditions. However, the situation drastically changes in nonequilibrium conditions, leading to Fröhlich's condensation, when the lifetime of a Davydov-like soliton is enormously enhanced, allowing for very long range propagation of signals. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 277-285 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We briefly describe a nonclassical nonlinear thermodynamic theory with statistical foundations. This statistical approach is based on a generalization to arbitrary nonequilibrium conditions of the Gibbs ensemble algorithm, the so-called nonequilibrium statistical operator method, which can be considered to be encompassed within the scope of Jaynes' predictive statistical physics. This emerging formalism is used to provide a study of the technoindustrial process of thermal stereolithography (or infrared-laser-induced rapid prototyping). The experimental results are interpreted and the technical requirements fundamental for the success of the process are pointed out.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 277-285, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 66 (1998), S. 177-187 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a mechanostatistical study of the so-called Fröhlich effect, namely nonthermal amplification of polar vibrations leading to complex behavior in biosystems, like biopolymers and large aggregates of macromolecules. Fröhlich condensation is considered to be of relevance for a certain class of biological processes, in particular in connection with the problem of long-range propagation of signals at physiological temperature. Resorting to a thermomechanical theory appropriate to deal with irreversible processes in systems far from equilibrium, earlier results are extended. We perform an analysis of the case when production of a double excitation of polar vibrations, generated by the action of an external pumping source of metabolic energy, is possible. It is shown that, when this is the case, the process involves a positive feedback mechanism that greatly facilitates and enhances the phenomenon of Fröhlich's condensation, and consequently the possible accompanying biological processes. The results are discussed and eventual connection with experimental observations pointed out.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 177-187, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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