9,391 research outputs found
Entropy and Entropy Production in Multiscale Dynamics
Heat conduction is investigated on three levels: equilibrium, Fourier, and
Cattaneo. The Fourier level is either the point of departure for investigating
the approach to equilibrium or the final stage in the investigation of the
approach from the Cattaneo level. Both investigations bring to the Fourier
level an entropy and a thermodynamics. In the absence of external and internal
influences preventing the approach to equilibrium the entropy that arises in
the latter investigation is the production of the classical entropy that arises
in the former investigation. If the approach to equilibrium is prevented, then
the entropy that arises in the investigation of the approach from the Cattaneo
level to the Fourier level still brings to the Fourier level the entropy and
the thermodynamics even if the classical entropy and the classical
thermodynamics is absent. We also note that vanishing total entropy production
as a characterization of equilibrium state is insufficient.Comment: Submitted to the Journal of Non-equilibrium Thermodynamic
Irreversible Thermodynamics in Multiscale Stochastic Dynamical Systems
This work extends the results of the recently developed theory of a rather
complete thermodynamic formalism for discrete-state, continuous-time Markov
processes with and without detailed balance. We aim at investigating the
question that whether and how the thermodynamic structure is invariant in a
multiscale stochastic system. That is, whether the relations between
thermodynamic functions of state and process variables remain unchanged when
the system is viewed at different time scales and resolutions. Our results show
that the dynamics on a fast time scale contribute an entropic term to the
"internal energy function", , for the slow dynamics. Based on the
conditional free energy , one can then treat the slow dynamics as if
the fast dynamics is nonexistent. Furthermore, we show that the free energy,
which characterizes the spontaneous organization in a system without detailed
balance, is invariant with or without the fast dynamics: The fast dynamics is
assumed to reach stationarity instantaneously on the slow time scale; they have
no effect on the system's free energy. The same can not be said for the entropy
and the internal energy, both of which contain the same contribution from the
fast dynamics. We also investigate the consequences of time-scale separation in
connection to the concepts of quasi-stationaryty and steady-adiabaticity
introduced in the phenomenological steady-state thermodynamics
Shock dynamics of phase diagrams
A thermodynamic phase transition denotes a drastic change of state of a physical system due to a continuous change of thermodynamic variables, as for instance pressure and temperature. The classical van der Waals equation of state is the simplest model that predicts the occurrence of a critical point associated with the gas-liquid phase transition. Nevertheless, below the critical temperature, theoretical predictions of the van der Waals theory significantly depart from the observed physical behaviour. We develop a novel approach to classical thermodynamics based on the solution of Maxwell relations for a generalised family of nonlocal entropy functions. This theory provides an exact mathematical description of discontinuities of the order parameter within the phase transition region, it explains the universal form of the equations of state and the occurrence of triple points in terms of the dynamics of nonlinear shock wave fronts
Combining Coarse-Grained Protein Models with Replica-Exchange All-Atom Molecular Dynamics
We describe a combination of all-atom simulations with CABS, a
well-established coarse-grained protein modeling tool, into a single multiscale
protocol. The simulation method has been tested on the C-terminal beta hairpin
of protein G, a model system of protein folding. After reconstructing atomistic
details, conformations derived from the CABS simulation were subjected to
replica-exchange molecular dynamics simulations with OPLS-AA and AMBER99sb
force fields in explicit solvent. Such a combination accelerates system
convergence several times in comparison with all-atom simulations starting from
the extended chain conformation, demonstrated by the analysis of melting
curves, the number of native-like conformations as a function of time and
secondary structure propagation. The results strongly suggest that the proposed
multiscale method could be an efficient and accurate tool for high-resolution
studies of protein folding dynamics in larger systems.Comment: 12 pages, 4 figure
Design of the Artificial: lessons from the biological roots of general intelligence
Our desire and fascination with intelligent machines dates back to the
antiquity's mythical automaton Talos, Aristotle's mode of mechanical thought
(syllogism) and Heron of Alexandria's mechanical machines and automata.
However, the quest for Artificial General Intelligence (AGI) is troubled with
repeated failures of strategies and approaches throughout the history. This
decade has seen a shift in interest towards bio-inspired software and hardware,
with the assumption that such mimicry entails intelligence. Though these steps
are fruitful in certain directions and have advanced automation, their singular
design focus renders them highly inefficient in achieving AGI. Which set of
requirements have to be met in the design of AGI? What are the limits in the
design of the artificial? Here, a careful examination of computation in
biological systems hints that evolutionary tinkering of contextual processing
of information enabled by a hierarchical architecture is the key to build AGI.Comment: Theoretical perspective on AGI (Artificial General Intelligence
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