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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Theoretical Physics

Mostrando recursos 1 - 20 de 60

  1. Universal theory of efficiency fluctuations

    Verley, Gatien; WILLAERT, Tim; VAN DEN BROECK, Christian; Esposito, Massimiliano
    Using the fluctuation theorem supplemented with geometric arguments, we derive universal features of the (long-time) efficiency fluctuations for thermal and isothermal machines operating under steady or periodic driving, close or far from equilibrium. In particular, the probabilities for observing the reversible efficiency and the least likely efficiency are identical to those of the same machine working under the time-reversed driving. For time-symmetric drivings, this reversible and the least probable efficiency coincide.

  2. Ensemble and trajectory thermodynamics: A brief introduction

    VAN DEN BROECK, Christian; Esposito, M.
    We revisit stochastic thermodynamics for a system with discrete energy states in contact with a heat and particle reservoir. (C) 2014 Elsevier B.V. All rights reserved.

  3. Dynamic range extension of hybridization sensors

    Hadiwikarta, W. W.; Carlon, E.; HOOYBERGHS, Jef
    In hybridization based nucleic acid sensors the stringency of hybridization poses a challenge to design and experiment. For a given set of experimental parameters the affinity window of probe target interaction is always limited and vice versa for a given probe set design, changes in experimental conditions can easily bring some measurements out of detection range. In this paper we introduce and apply a strategy to extend this dynamic range for affinity sensors, sensors which measure the amount of hybridized molecules after equilibrium is reached. The method relies on concepts of additivity of nucleic acids hybridization free energies and on...

  4. Echo states for detailed fluctuation theorems

    BECKER, Thijs; WILLAERT, Tim; CLEUREN, Bart; VAN DEN BROECK, Christian
    Detailed fluctuation theorems are statements about the probability distribution for the stochastic entropy production along a trajectory. It involves the consideration of a suitably transformed dynamics, such as the time reversed, the adjoint, or a combination of these. We identify specific, typically unique, initial conditions, called echo states, for which the final probability distribution of the transformed dynamics reproduces the initial distribution. In this case the detailed fluctuation theorems relate the stochastic entropy production of the direct process to that of the transformed one. We illustrate our results by an explicit analytical calculation and numerical simulations for a modulated two-state...

  5. Adsorption and desorption in confined geometries: A discrete hopping model

    BECKER, Thijs; NELISSEN, Kwinten; CLEUREN, Bart; PARTOENS, Bart; VAN DEN BROECK, Christian
    We study the adsorption and desorption kinetics of interacting particles moving on a one-dimensional lattice. Confinement is introduced by limiting the number of particles on a lattice site. Adsorption and desorption are found to proceed at different rates, and are strongly influenced by the concentration-dependent transport diffusion. Analytical solutions for the transport and self-diffusion are given for systems of length 1 and 2 and for a zero-range process. In the last situation the self- and transport diffusion can be calculated analytically for any length.

  6. The unlikely Carnot efficiency

    Verley, Gatien; Esposito, Massimiliano; WILLAERT, Tim; VAN DEN BROECK, Christian
    The efficiency of an heat engine is traditionally defined as the ratio of its average output work over its average input heat. Its highest possible value was discovered by Carnot in 1824 and is a cornerstone concept in thermodynamics. It led to the discovery of the second law and to the definition of the Kelvin temperature scale. Small-scale engines operate in the presence of highly fluctuating input and output energy fluxes. They are therefore much better characterized by fluctuating efficiencies. In this study, using the fluctuation theorem, we identify universal features of efficiency fluctuations. While the standard thermodynamic efficiency is,...

  7. Transient behaviour of a polymer dragged through a viscoelastic medium

    VANDEBROEK, Hans; VANDERZANDE, Carlo
    We study the dynamics of a polymer that is pulled by a constant force through a viscoelastic medium. This is a model for a polymer being pulled through a cell by an external force, or for an active biopolymer moving due to a self-generated force. Using the Rouse model with a memory dependent drag force, we find that the center of mass of the polymer follows a subballistic motion. We determine the time evolution of the length and the shape of the polymer. Through an analysis of the velocity of the monomers, we investigate how the tension propagates through the...

  8. Diffusion of interacting particles in discrete geometries: Equilibrium and dynamical properties

    BECKER, Thijs; NELISSEN, Kwinten; CLEUREN, Bart; Partoens, Bart; VAN DEN BROECK, Christian
    We expand on a recent study of a lattice model of interacting particles [Phys. Rev. Lett. 111, 110601 (2013)]. The adsorption isotherm and equilibrium fluctuations in particle number are discussed as a function of the interaction. Their behavior is similar to that of interacting particles in porous materials. Different expressions for the particle jump rates are derived from transition-state theory. Which expression should be used depends on the strength of the interparticle interactions. Analytical expressions for the self- and transport diffusion are derived when correlations, caused by memory effects in the environment, are neglected. The diffusive behavior is studied numerically...

  9. Work statistics in stochastically driven systems

    Verley, Gatien; VAN DEN BROECK, Christian; Esposito, Massimiliano
    We identify the conditions under which a stochastic driving that induces energy changes into a system coupled with a thermal bath can be treated as a work source. When these conditions are met, the work statistics satisfy the Crooks fluctuation theorem traditionally derived for deterministic drivings. We illustrate this fact by calculating and comparing the work statistics for a two-level system driven respectively by a stochastic and a deterministic piecewise constant protocol.

  10. Stochastic thermodynamics: A brief introduction

    VAN DEN BROECK, Christian
    The main purpose of statistical mechanics is to give a microscopic derivation of macroscopic laws, including in particular the celebrated second law of thermodynamics. In recent years, there have been spectacular developments in this respect, including the integral and detailed work fluctuation theorems and the theory of stochastic thermodynamics. Here we give a brief introduction to these developments. In the first step, we derive the first and second law of thermodynamics for a Markovian stochastic process at the ensemble level, including two major advances: 1) the theory can be applied to small-scale systems including the effect of fluctuations, 2) the...

  11. Stochastic functionals and fluctuation theorem for multikangaroo processes

    VAN DEN BROECK, Christian; Toral, R.
    We introduce multikangaroo Markov processes and provide a general procedure for evaluating a certain type of stochastic functional. We calculate analytically the large deviation properties. We apply our results to zero-crossing statistics and to stochastic thermodynamics, including the derivation of the fluctuation theorem and the large deviation properties for the stochastic entropy production in a typical solid state device.

  12. EmpaTeX 2014 ??? workshop results

    Van den Bergh, Jan; Matton, Mike; WILLAERT, Koen; Luyten, Kris

  13. Efficiency at maximum power in the low-dissipation limit

    Van den Broeck, Christian
    We present a general thermodynamic framework for the low-dissipation limit. In the case of an iso-thermal engine, which converts chemical work into mechanical work, this theory predicts an efficiency at maximum power eta* identically equal to 1/2. For multi-bath thermal machines, we derive bounds for efficiency at maximum power, namely eta(rev)/2 <= eta* <= eta(rev)/(2-eta(rev)), where eta(rev) is the efficiency of the corresponding reversible scenario.

  14. Comment on "Cooling by Heating: Refrigeration Powered by Photons'' Reply

    Cleuren, B.; Rutten, B.; Van den Broeck, C.
    Physics, Multidisciplinary

  15. Publisher's Note: “Efficiency at maximum power of a chemical engine” [J. Chem. Phys.139, 134111 (2013)]

    Hooyberghs, Hans; CLEUREN, Bart; Salazar, Alberto; Indekeu, Joseph O.; VAN DEN BROECK, Christian

  16. 1 st Workshop on Empathic Television Experiences (EmpaTeX 2014)

    VAN DEN BERGH, Jan; LUYTEN, Kris; Matton, Mike; WILLAERT, Koen
    Empathy is a key ingredient in effective human-to-human communication but is hardly explored in HCI beyond the field of social robotics and virtual agents Current technology is to some extend able to measure expression of people’s emotions using a variety of sensors, which is essential but not sufficient to create an empathic experience. The goal of this workshop is to investigate what empathy can mean within the context of ITV experiences and how to create/design interactive experiences that are recognized by TV viewers as being empathic. The workshop will be a forum to discuss different enabling technologies, promising application architectures...

  17. Fluctuation symmetry in a two-state Markov model

    WILLAERT, Tim; CLEUREN, Bart; VAN DEN BROECK, Christian
    We show that the scaled cumulant generating and large deviation function, associated to a two-state Markov process involving two processes, obey a symmetry relation reminiscent of the fluctuation theorem, independent from any conditions on the transition rates. The Legendre transform leading from the scaled cumulant generating function to the large deviation function is performed in an ingenious way, avoiding the sign problem associated to taking a square root. Applications to the theory of random walks and to the stochastic thermodynamics for a quantum dot are presented.

  18. Large deviation function and fluctuation theorem for classical particle transport

    Harbola, Upendra; VAN DEN BROECK, Christian; Lindenberg, Katja
    We analytically evaluate the large deviation function in a simple model of classical particle transfer between two reservoirs. We illustrate how the asymptotic long-time regime is reached starting from a special propagating initial condition. We show that the steady-state fluctuation theorem holds provided that the distribution of the particle number decays faster than an exponential, implying analyticity of the generating function and a discrete spectrum for its evolution operator.

  19. Gene expressions changes in bronchial epithelial cells: Markers for respiratory sensitizers and exploration of the NRF2 pathway

    Remy, Sylvie; Verstraelen, Sandra; Van Den Heuvel, Rosette; Nelissen, Inge; Lambrechts, Nathalie; HOOYBERGHS, Jef; Schoeters, Greet
    For the classification of respiratory sensitizing chemicals, no validated in vivo nor in vitro tests are currently available. In this study, we evaluated whether respiratory sensitizers trigger specific signals in human bronchial epithelial (BEAS-2B) cells at the level of the transcriptome. The cells were exposed during 6, 10, and 24 h to 4 respiratory sensitizers and 6 non-respiratory sensitizers (3 skin sensitizers and 3 respiratory irritants) at a concentration inducing 20% cell viability loss after 24 h. Changes in gene expression were evaluated using Agilent Whole Human Genome 4 44 K oligonucleotide arrays. A limited number of 11 transcripts could...

  20. Targeted resequencing of HIV variants by microarray thermodynamics

    Hadiwikarta, Wahyu W.; Van Dorst, Bieke; Hollanders, Karen; Stuyver, Lieven; Carlon, Enrico; HOOYBERGHS, Jef
    Within a single infected individual, a virus population can have a high genomic variability. In the case of HIV, several mutations can be present even in a small genomic window of 20-30 nucleotides. For diagnostics purposes, it is often needed to resequence genomic subsets where crucial mutations are known to occur. In this article, we address this issue using DNA microarrays and inputs from hybridization thermodynamics. Hybridization signals from multiple probes are analysed, including strong signals from perfectly matching (PM) probes and a large amount of weaker cross-hybridization signals from mismatching (MM) probes. The latter are crucial in the data...

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