arXiv subjects

D. Lairez

Publications and source records attributed to D. Lairez.

9 recordsLinked to original sources

arXiv2024

Thermostatistics, information, subjectivity, why is this association so disturbing?

Although information theory resolves inconsistencies (known under the form of famous enigmas) of the traditional approach of thermostatistics, its place in the corresponding literature is not what it deserves. This article supports the idea that this is mainly due to epistemological rather than scientific reasons: the subjectivity introduced into physics is perceived as a problem. Here is an attempt to expose and clarify where exactly this subjectivity lies: in the representation of the reality and in probabilistic inference. Two aspects which have been integrated into the practice of science for a long time and which should no longer frighten anyone, but which become explicit with information theory.

physics.soc-ph↗

arXiv2024

On the supposed mass of entropy and that of information

In the theory of special relativity, energy can be found in two forms: kinetic energy and rest mass. Potential energy of a body is actually stored under the form of rest mass, interaction energy too, temperature is not. Information acquired about a dynamical system can be potentially used to extract useful work from it. Hence the "mass-energy-information equivalence principle" that has been recently proposed. In this paper, it is first recalled that for a thermodynamic system made of non interacting entities at constant temperature, the internal energy is also constant. So that, the energy involved in a variation of entropy ($TΔS$) differs from a change in potential energy stored or released and cannot be associated to a corresponding variation of mass of the system, even if it is expressed in term of quantity of information. This debate gives us the opportunity to deepen the notion of entropy seen as a quantity of information, to highlight the difference between logical irreversibility (a state dependent property) and thermodynamical irreversibility (a path dependent property) and to return to the nature of the link between energy and information that is dynamical.

physics.gen-ph↗

arXiv2023

Thermodynamical versus logical irreversibility: a concrete objection to Landauer's principle

Landauer's principle states that the logical irreversibility of an operation, such as erasing one bit, whatever its physical implementation, necessarily implies its thermodynamical irreversibility. In this paper, a very simple counterexample of physical implementation (that uses a two-to-one relation between logic and thermodynamic states) is given that allows to erase one bit in a thermodynamical quasistatic manner (i.e. that may tend to be reversible if slowed down enough).

physics.class-ph↗

arXiv2016

The concept of entropic rectifier facing experiments

The transport of molecules in confined media is subject to entropic barriers. So theoretically, asymmetry of the confinement length may lead to molecular ratchets with entropy as the only driving force for the biased transport. We address experimentally this question by performing alternative ionic current measurements on electrolytes confined in neutral conical nanopores. In case anions and cations widely differ in size, we show that rectification of ionic current can be obtained that depends on ions size and cycle frequency, consistently with the entropic ratchet mechanism.

cond-mat.soft↗

arXiv2013

Peptide pores in lipid bilayers : voltage facilitation pleads for a revised model

We address the problem of antimicrobial peptides that create pores in lipid bilayers, focusing on voltage-temperature dependence of pore opening. Two novel experiments (voltage-clamp with alamethicin as an emblematic representative of these peptides and neutron reflectivity of lipid-monolayer at solid/water interface under electric field) serve to revise the only current theoretical model (H. W. Huang et al.Phys. Rev. Lett., 92, 198304 (2004)). We introduce a general contribution of the electric field as being responsible for an unbalanced tension of the two bilayer leaflets and we claim that the main entropy cost of one pore opening is due to the corresponding "excluded-area" for lipid translation.

cond-mat.soft↗

arXiv2012

Crowding effect on helix-coil transition: beyond entropic stabilization

We report circular dichroism measurements on the helix-coil transition of poly(L-glutamic acid) in solution with polyethylene glycol (PEG) as a crowding agent. Using small angle neutron scattering, PEG solutions have been characterized and found to be well described by the picture of a transient network of mesh size $ξ$, usual for semi-diluted chains in good solvent. We show that the increase of PEG concentration stabilizes the helices and increases the transition temperature. But more unexpectedly we also notice that the increase of crowding agent concentration reduces the mean helix extent at the transition, or in other words reduces its cooperative feature. This result cannot be accounted for by an entropic stabilization mechanism. Comparing the mean length of helices at the transition and the mesh size of the PEG network, our results strongly suggest two regimes: helices shorter or longer than the mesh size.

cond-mat.soft↗

arXiv2012

Slow and remanent electric polarization of adsorbed BSA layer evidenced by neutron reflection

Using neutron reflectivity together with an appropriate electrochemical cell, we have studied the effects of transverse electric field on the Bovine Serum Albumin (BSA) monolayer initially adsorbed at the interface of the aqueous solution and a conductive doped-silicon wafer. Depending on the sign of the initial potential, a second layer is adsorbed on top of the first whereas a subsequent reversal of potential has no effect. We show that this behavior reveals the slow and remanent electric polarization of the first BSA layer and suggest an analogy with spin glasses based on the dipolar structure of this protein.

cond-mat.soft↗

arXiv2010

Pink noise of ionic conductance through single artificial nanopores revisited

We report voltage-clamp measurements through single conical nanopore obtained by chemical etching of a single ion-track in polyimide film. Special attention is paid on the pink noise of the ionic current (i.e. $1/f$ noise) measured with different filling liquids. The relative pink noise amplitude is almost independent of concentration and pH for KCl solutions, but varies strongly using ionic liquids. In particular we show that depending on the ionic liquid, the transport of charge carriers is strongly facilitated (low noise and higher conductivity than in the bulk) or jammed. These results show that the origin of the pink noise can be ascribed neither to fluctuations of the pore geometry nor to the pore wall charges but rather to a cooperative effect on ions motion.

cond-mat.soft↗

arXiv2004

Pacman percolation: a model for enzyme gel degradation

We study a model for the gel degradation by an enzyme, where the gel is schematized as a cubic lattice, and the enzyme as a random walker, that cuts the bonds over which it passes. The model undergoes a (reverse) percolation transition, which for low density of enzymes falls in a universality class different from random percolation. In particular we have measured a gel fraction critical exponent beta=1.0+-0.1, in excellent agreement with experiments made on the real system.

cond-mat.soft↗