1,721,020 research outputs found
Efficiency at maximum power of interacting molecular machines
No full textWe investigate the efficiency of systems of molecular motors operating at maximum power. We consider two models of kinesin motors on a microtubule: for both the simplified and the detailed model, we find that the many-body exclusion effect enhances the efficiency at maximum power of the many-motor system, with respect to the single motor case. Remarkably, we find that this effect occurs in a limited region of the system parameters, compatible with the biologically relevant range
Heat transport in harmonic oscillator systems with thermal baths: application to optomechanical arrays
Full text linkWe investigate the transport of phonons between N harmonic oscillators in contact with independent thermal baths and coupled to a common oscillator, and derive an expression for the steady state heat flow between the oscillators in the weak coupling limit. We apply these results to an optomechanical array consisting of a pair of mechanical resonators coupled to a single quantized electromagnetic field mode by radiation pressure as well as to thermal baths with different temperatures. In the weak coupling limit this system is shown to be equivalent to two mutually-coupled harmonic oscillators in contact with an effective common thermal bath in addition to their independent baths. The steady state occupation numbers and heat flows are derived and discussed in various regimes of interest.</p
Reconstructing the free energy landscape of a mechanically unfolded model protein
No full textThe equilibrium free-energy landscape of an off-lattice model protein as a function of an internal
(reaction) coordinate is reconstructed from out-of-equilibrium mechanical unfolding manipulations. This
task is accomplished via two independent methods: by employing an extended version of the Jarzynski
equality (EJE) and the protein inherent structures (ISs). In a range of temperatures around the ‘‘folding
transition’’ we find a good quantitative agreement between the free energies obtained via EJE and IS
approaches. This indicates that the two methodologies are consistent and able to reproduce equilibrium
properties of the examined system. Moreover, for the studied model the structural transitions induced by
pulling can be related to thermodynamical aspects of folding
Sisyphus effect in pulse-coupled excitatory neural networks with spike-timing-dependent plasticity
No full textThe collective dynamics of excitatory pulse-coupled neural networks with spike-timing-dependent plasticity (STDP) is studied. Depending on the model parameters stationary states characterized by high or low synchronization can be observed. In particular, at the transition between these two regimes, persistent irregular low frequency oscillations between strongly and weakly synchronized states are observable, which can be identified as infraslow oscillations with frequencies ≃0.02-0.03 Hz. Their emergence can be explained in terms of the Sisyphus effect, a mechanism caused by a continuous feedback between the evolution of the coherent population activity and of the average synaptic weight. Due to this effect, the synaptic weights have oscillating equilibrium values, which prevents the neuronal population from relaxing into a stationary macroscopic state
Exact fluctuation theorem without ensemble quantities
Full text linkpeer reviewedEvaluating the entropy production (EP) along a stochastic trajectory requires the knowledge of the system probability distribution, an ensemble quantity notoriously difficult to measure. In this letter, we show that the EP of nonautonomous systems in contact with multiple reservoirs can be expressed solely in terms of physical quantities measurable at the single trajectory level with a suitable preparation of the initial condition. As a result, we identify universal energy and particle fluctuation relations valid for any measurement time. We apply our findings to an electronic junction model which may be used to verify our prediction experimentally
Emergence of slow collective oscillations in neural networks with spike-timing dependent plasticity
No full textThe collective dynamics of excitatory pulse coupled neurons with spike timing dependent plasticity (STDP) is studied. The introduction of STDP induces persistent irregular oscillations between strongly and weakly synchronized states, reminiscent of brain activity during slow-wave sleep. We explain the oscillations by a mechanism, the Sisyphus Effect, caused by a continuous feedback between the synaptic adjustments and the coherence in the neural firing. Due to this effect, the synaptic weights have oscillating equilibrium values, and this prevents the system from relaxing into a stationary macroscopic state
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