Didier Lairez

Atomic Energy and Alternative Energies Commission | CEA

Landauer's "principle" claims that erasing one bit of information necessarily dissipates at least Tln2 of heat into the surroundings, making a possibly logically irreversible operation also thermodynamically irreversible. It is commonly accepted that this result is a fundamental principle of physics that definitively establishes the link between in...

Although information theory resolves the inconsistencies (known in 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...

In the theory of special relativity, energy can be found in two forms: kinetic energy and rest mass. The potential energy of a body is actually stored in the form of rest mass, the interaction energy too, but temperature is not. Information acquired about a dynamical system can be potentially used to extract useful work from it. Hence, the mass–ene...

In statistical mechanics, the generally called Stirling approximation is actually an approximation of Stirling’s formula. In this article, it is shown that the term that is dropped is in fact the one that takes fluctuations into account. The use of the Stirling’s exact formula forces us to reintroduce them into the already proposed solutions of wel...

Among classical nanoporous oxide membranes, anodic aluminum oxide (AAO) membranes, made of non-connected, parallel and ordered nanochannels, are very interesting nanoporous model systems widely used for multiple applications. Since most of these applications involve local phenomena at the nanochannel surface, the fine description of the electrical...

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...

Among classical nanoporous oxide membranes, anodic aluminum oxide (AAO) membranes, made of non-connected, parallel and ordered nanochannels, are very interesting nanoporous model systems widely used for multiple applications. Since most of these applications involve local phenomena at the nanochannel surface, the fine description of the electrical...

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 letter, a very simple counterexample of physical implementation (that uses a two-to-one relation between logic and thermodynamic states) is give...

In statistical mechanics, the generally called Stirling approximation is actually an approximation of Stirling's formula. In this article, it is shown that the term that is dropped is in fact the one that takes fluctuations into account. The use of the Stirling's exact formula forces us to reintroduce them into the already proposed solutions of wel...

Introducing the Boltzmann distribution very early in a statistical thermodynamics course (in the spirit of Feynmann) has many didactic advantages, in particular that of easily deriving the Gibbs entropy formula. In this note, a short derivation is proposed from the fundamental postulate of statistical mechanics and basics calculations accessible to...

Even today, the concept of entropy is perceived by many as quite obscure. The main difficulty is analyzed as being fundamentally due to the subjectivity and anthropocentrism of the concept that prevent us to have a sufficient distance to embrace it. However, it is pointed out that the lack of coherence of certain presentations or certain preconceiv...

When a lipid membrane approaches a material/nanomaterial, nonspecific adhesion may occur. The interactions responsible for nonspecific adhesion can either preserve the membrane integrity or lead to its disruption. Despite the importance of the phenomenon, there is still a lack of clear understanding of how and why nonspecific adhesion may originate...

The myelin sheath—a multi-double-bilayer membrane wrapped around axons—is an essential part of the nervous system which enables rapid signal conduction. Damage of this complex membrane system results in demyelinating diseases such as multiple sclerosis (MS). The process in which myelin is generated in vivo is called myelination. In our study, we in...

It remains a great experimental challenge to obtain quantitative information on the polyelectrolyte (PE) behavior confined in charged nanoporous materials. Here, we propose an original approach using transverse streaming potential measurements (TSPMs), an efficient technique providing information on the electrical surface properties of nanoporous m...

The exact resolution function of the transfer vector for the HERMÈS reflectometer at the Laboratoire Léon Brillouin is calculated as an example of a neutron time-of-flight spectrometer with a double-disk chopper. The calculation accounts for the wavelength distribution of the incident beam, the tilt of the chopper axis, collimation and gravity, wit...

The binding of imidazolium salts to cucurbit[8]uril, CB[8], triggers a step-wise self-assembly process with semiflexible polymer chains and crystalline nanostructures as early- and late-stage species, respectively. In such a process, which involves the crystallization of the host–guest complexes, the guest plays a critical role in directing self-as...

The exact resolution function in transfer vector for the reflectometer HERM\`ES at Laboratoire L\'eon Brillouin is calculated as an example of neutron time-of-fligh spectrometer with double-disk chopper. Calculation accounts for wavelength distribution of the incident beam, tilt of the chopper axis, collimation and gravity, without approximation of...

During evaporative drying of a colloidal dispersion, the structural behavior at the air-dispersion interface is of particular relevance to the understanding of the consolidation mechanism and the final structural and mechanical properties of the porous media. The drying interface constitutes the region of initial drying stress that, when accumulate...

Nanoparticles (NPs) homogeneously covered with polymer chains or with chains of two different polymers segregated in distinct domains (“Janus” particles) possess remarkable features. Their unique colloidal properties can be finely tuned by the grafted polymers while the characteristics of the nano-core remain unaffected. Herein, a simple and robust...

The formation of supported lipid bilayers (SLB) on hydrophilic substrates through the method of unilamelar vesicle fusion is used routinely in a wide range of biophysical studies. In an effort to control and better understand the fusion process on the substrate, many experimental studies employing different techniques have been devoted to the eluci...

Ionic Liquids (ILs) are a specific class of molecular electrolytes characterized by the total absence of co-solvent. Due to their remarkable chemical and electrochemical stability, they are prime candidates for the development of safe and sustainable energy storage systems. The competition between electrostatic and van der Waals interactions leads...

As opposed to piezo-ceramics (i.e PZT), flexibility and robustness characterize piezoelectric polymers. The main advantage of a piezoelectric polymer, such as Poly (vinylidene fluoride) (PVDF), is an electric power generation under large reversible elastic deformation. Starting from polarized PVDF, we have shown that, despite the fact that irradiat...

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 n...

Conical nanopores can theoretically work as molecular funnel based on an entropic ratchet mechanism. This may allow to rectify ionic current in case anions and cations widely differ in size. We address experimentally this question by performing cyclic voltammetry on electrically neutral conical nanopores ("track-etched" membranes at the isoelectric...

Phenol-functionalized MWCNTs were prepared by specially synthesized "wet chemistry" process. TEM images revealed that the produced carbon nanotubes are of high purity having diameter from 20 to 45. nm and length 2-3. μm. In order to optimize the utilization of MWCNTs for the preparation of mixed matrix composite materials a thorough characterizatio...

To study the impact of the size and the structure of the nano-assembly on the drug/particle association, determining the intrinsic partition coefficient, in order to better master the encapsulation and release properties of the carrier. An experimental methodology is proposed to characterize the drug/nanoparticle association by mean of a partition...

The effects of the thermoelastic and piezoelectric strain exerted by an active polymer matrix on a Ni nanowire (NW) are studied at the nanoscale by measuring the inverse magnetostriction of single-contacted Ni NWs. The reorientation of the magnetization is measured by anisotropic magnetoresitance. In the absence of strain, the Ni NW exhibits a typi...

Abstract In a cylindrical magnetic nanowire, a magnetic domain wall (DW) can move along the wire when an applied magnetic field or a spin-polarized current is applied. We show that in a magnetic device composed of two conical nanowires connected by a nanosized constriction, a DW can be trapped and detrapped. The magnetoreistance and the relaxation...

DOI:https://doi.org/10.1103/PhysRevLett.111.139904

Herein we report the photocontrol of the CB[8] mediated supramolecular polymerization of azobenzene-containing monomers. The CB[8] polymers have been characterized both in solution and in the solid state. These host-guest complexes can be reversibly switched between high thermostable photostationary states. Moreo...

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...

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. The PEG solutions have been characterized by small angle neutron scattering and are well described by the picture of a network of mesh size ξ, usual for semi-dilute chains in good solvent. W...

The optical properties of a series of gold nanoparticles (D ≈ 2.3–8 nm) grafted with a stabilizing polymer with a wide range of chain lengths (Mw ≈ 6.5K–29.5K) have been studied quantitatively in different dielectric solvents. Mie–Drude dipolar theory was applied to model the localized surface plasmon resonance (SPR) peak position, as well as the p...

In the present study, [bmim][PF6] ionic liquid (IL) was introduced into the pores of two ordered mesoporous silicas (MCM-41 and SBA-15) having different pore sizes by means of two different processes: a) with physical imbibition from a methanol solution under high vacuum and b) by chemically immobilising the IL with silanisation of the pore surface...

Tissues and organs are formed by specialized cells and by extracellular matrix (ECM) organized in 3-dimensional (3D) structure. ECM is a mix of various components, mainly of proteins. ECM remodeling is a physiological and pathological phenomenon (Raeber et al 2005). During tumor dissemination, invasive cells must liquefy the matrix to invade other...

Small-angle neutron scattering (SANS), contrast-matching SANS, and nitrogen adsorption have been utilized to investigate the confined ionic liquid (IL) [bmim][PF(6)] phase in ordered mesoporous silica MCM-41 and SBA-15. The results suggest that the pores of SBA-15 are completely filled with IL whereas a small fraction of the pore volume, the pore "...

Track-etched functionalized nanoporous β-PVDF membrane electrodes, or functionalized membrane electrodes (FMEs), are electrodes made from track-etched, poly(acrylic acid) (PAA) functionalized nanoporous β-poly(vinylidene fluoride) (β-PVDF) membranes with thin porous Au films sputtered on each side as electrodes. In order to form the β-PVDF nanoporo...

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 adsorbe...

Angiogenesis plays a critical role in tumor growth. This phenomena is regulated by numerous mediators such as vascular endothelial growth factor (VEGF). CBO-P11, a cyclo-peptide, has proven to specifically bind to receptors of VEGF and may be used as targeting ligand for tumor angiogenesis. We herein report the design of novel nanoparticles conjuga...

Small-angle neutron scattering proved that molecules in aqueous solutions of pyridine, 2-methylpyridine and 2,6-dimethylpyridine form clusters. The clusters are dynamic aggregates consisting of hydrogen-bonded water-amine complexes. Strengthening of the hydrogen bonds between water and amine molecules due to the methyl groups in the ortho position...

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 to 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...

Voltage-clamp measurements on lipid bilayers at the onset of peptide attacks before pore formation are reported. With four different peptides [alamethicin, melittin, and two synthetic peptides of the leucine (L)-lysine(K) copolymers (LK series)], correlations of conductivity fluctuations slowly decay over four decades in time. This slow dynamics is...

The supramolecular organization of particles composed of heteroxylans (HX) and synthetic lignin (dehydrogenation polymer, DHPs) was studied by light scattering (LS), atomic force microscopy (AFM), and fluorescent probes. Results from static and quasi-elastic light scattering indicate a dense core surrounded by a soft corona. Such organization is al...

The main characteristics of the very small angle neutron scattering spectrometer (VSANS) under construction at the Laboratoire Léon Brillouin are a multibeam pinhole collimator converging onto an image plate detector. By combining tiny collimation (diaphragms of around 1 or 2 mm in diameter) with the small pixel size of the detector (0.15 × 0.15 mm...

Poly(vinylidene fluoride) (β-PVDF) nanoporous membranes are obtained by heavy ion irradiation and track etching leading to cylindrical pores. Pores diameter measured by scanning electron microscopy and small angle neutron scattering lies in the 20–50nm range. Electron paramagnetic resonance study gives evidence that radicals still remains in PVDF m...

Enzyme-catalyzed gel degradation is inherently controlled by diffusion of enzymes in the gel. We report kinetics measurements on the gelatin-thermolysin system, varying solvent viscosity as well as gel and enzyme concentrations. Scaling relations and reduced variables are proposed which are shown to account for the experimental results. Finally, we...

We study the electrophoretic blockades due to entries of partially unfolded proteins into a nanopore as a function of the concentration of the denaturing agent. Short and long pore blockades are observed by electrical detection. Short blockades are due to the passage of completely unfolded proteins, their frequency increases as the concentration of...

Small-angle neutron scattering has been successfully used since the 1970s. As a general rule, methods to extract the useful signal from that received by the detector are well known and give good results. At the Laboratoire Léon Brillouin, for example, these methods have been employed for a long time. However, the data reduction software has been ch...

T4 DNA semi-dilute entangled solutions submitted to high shear rates show a region of weak dependence of the steady-state shear stress on the shear rate. For the highest concentration studied, this region extends over two decades of shear rate, and a plateau of shear stress is observed over one decade. The concentration dependence of the lower boun...

La diffusion de neutrons aux petits angles (DNPA) permet de sonder les propriétés statiques de la matière sur une échelle spatiale allant de quelques dixièmes à quelques dizaines de nanomètres. Cette technique est ainsi particulièrement bien adaptée à l'étude des macromolécules en solution. Il est possible d'accéder à des grandeurs moyennes qui car...

In order to mimic the first steps of lignification, pectin/synthetic lignin (dehydrogenation polymers (DHPs)) interactions were investigated using reconstructing approaches. In artificially lignified bacterial cellulose(BC)/pectin composites, DHP nodules display a more dispersed distribution than in BC mats. Occurrence of covalent linkages between...

Coniferyl alcohol was polymerized in pectin solution in order to mimic the lignification that is the final step of biosynthesis of plant cell wall. Dehydrogenated polymers (DHP = coniferyl alcohol polymers = synthetic lignin) interact with pectin to form hydrophobic clusters as monitored by pyrene fluorescence spectroscopy. The structure of these c...

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 bond over which it passes was studied. The model was found to undergo a reverse random percolation which, for low density enzymes falls within a universality class different from random percolation. The cha...

Enzyme-catalyzed proteolysis of gelatin gels has been studied. We report a gel degradation rate varying as the square of the enzyme concentration. The diffusion motion of enzymes in the gel has been measured by two-photon fluorescence correlation spectroscopy and identified as being anomalously slow. These experimental results are discussed from a...

Small-angle neutron scattering experiments were performed on dilute solutions of a high molecular weight protein (fibronectin, M = 580 kg/mol) in four cases: native conditions; unfolded state obtained by a denaturing agent (urea); and two badly refolded (or collapsed) states obtained by progressive elimination of the denaturing agent in salt-contai...

Fibronectin structural reorganization induced by temperature has been investigated by Fourier-transform infrared (FT-IR) spectroscopy and light-scattering experiments. At 20 degrees C, from resolution enhanced by FT-IR spectra, 43% of beta sheet, 31% of turn and 26% of unordered structures were estimated. Static and quasi-elastic light-scattering r...

Fibronectin structural reorganization induced by temperature has been investigated by Fourier-transform infrared (FT-IR) spectroscopy and light-scattering experiments.At 20 °C, from resolution enhanced by FT-IR spectra, 43% of β sheet, 31% of turn and 26% of unordered structures were estimated. Static and quasi-elastic light-scattering results do n...

The use of spherical probe particles to investigate the viscoelastic properties of polymer solutions has been suggested for a long time. We present, in this paper, an analysis of quasi-elastic light scattering results from latex probe particles during gelation of a gelatin solution. We show that by focusing on the short-time and long-time behavior...

We have studied by quasi-elastic light scattering the aggregation of hen egg-white lysozyme upon salt addition. Our results show that these aggregates are fractal, in agreement with the results reported in the literature, and that they do not display any fluctuation of internal concentration. Lysozyme aggregates are rigid at the time scale consider...

We report a quasielastic light scattering study of the dynamics of large latex probe particles (R=225 nm) in gelatin solution undergoing gelation. We show that by focusing on the short-time and long-time behavior of the autocorrelation function, it is possible to simply interpret out data in terms of the divergence of the viscosity and emergence of...

We monitored the cell-free solubilization of extracellular matrix and fibronectin gels, catalyzed by exogenous proteinases. The corresponding measurements could not be interpreted according to usual proteinase kinetics. The observation that this experimental system did not consist in surface but in bulk degradation and appeared specific to gel subs...

Water confined in nonionic fluorocarbon reverse micelles was investigated through mid-infrared spectroscopy (OH stretching and bending modes), in combination with quasielastic light scattering data. The characteristic OH stretching band is seen to exhibit significant changes upon decreasing water core size. An analysis in terms of three different l...

Aggregation of methylcellulose in aqueous dilute solution is studied by light and small angle neutron scattering. For temperature T<293.15K, the free chains adopt a swollen conformation. For T>313.15K, a slow aggregation kinetics occurs. At qRg<1, the association number is found to vary as Rg3. However at qRg>1, the scattered intensity decreases as...

Fibronectin is a multifunctional glycoprotein (molecular mass, M = 530 kg/mol) of the extra cellular matrix (ECM) having a major role in cell adhesion. In physiological conditions, the conformation of this protein still remains debated and controversial. Here, we present a set of results obtained by scattering experiments. In "native" conditions, t...

The aggregation of hen egg-white lysozyme upon salt addition was studied by quasi-elastic light scattering. Our results agree with the fractal structure of the aggregates already reported in the literature. However, we also demonstrate that these aggregates are rigid, since they do not display any fluctuation of internal concentration. Such a r...