Transport of long neutral polymers in the semidilute regime through a protein nanopore

We investigate the entrance of single poly(ethylene glycol) chains into an α-hemolysin channel. We detect the frequency and duration of the current blockades induced by large neutral polymers, where chain radius is larger than pore diameter. In the semidilute regime, these chains pass only if the monomer concentration is larger than a well-defined threshold. Experiments are performed in a very large domain of concentration and molecular mass, up to 35% and 200 kDa, respectively, which was previously unexplored. The variation of the dwell time as a function of molecular mass shows that the chains are extracted from the semidilute solution in contact with the pore by a reptation mechanism.     

Distances in evidence theory: Comprehensive survey and generalizations

The purpose of the present work is to survey the dissimilarity measures defined so far in the mathematical framework of evidence theory, and to propose a classification of these measures based on their formal properties. This research is motivated by the fact that while dissimilarity measures have been widely studied and surveyed in the fields of probability theory and fuzzy set theory, no comprehensive survey is yet available for evidence theory. The main results presented herein include a synthesis of the properties of the measures defined so far in the scientific literature; the generalizations proposed naturally lead to additions to the body of the previously known measures, leading to the definition of numerous new measures. Building on this analysis, we have highlighted the fact that Dempster’s conflict cannot be considered as a genuine dissimilarity measure between two belief functions and have proposed an alternative based on a cosine function. Other original results include the justification of the use of two-dimensional indexes as (cosine; distance) couples and a general formulation for this class of new indexes. We base our exposition on a geometrical interpretation of evidence theory and show that most of the dissimilarity measures so far published are based on inner products, in some cases degenerated. Experimental results based on Monte Carlo simulations illustrate interesting relationships between existing measures.     

Smart Foams: Switching Reversibly between Ultrastable and Unstable Foams

Smart foams: Ultrastable foams with an optimal foamability are obtained using hydroxy fatty acids tubes. The stabilization results from the adsorption of monomers at the air-water interface and from the presence of tubes in the plateau borders. Upon heating, tubes transform to micelles, leading to foam destabilization and thus to the first foams to exhibit temperature-tuneable stability.     

Bubble cell for magnetic bead trapping in capillary electrophoresis

A bubble cell capillary classically used to extend the optical path length for UV–vis detection is employed here to trap magnetic beads. With this system, a large amount of beads can be captured without inducing a strong pressure drop, as it is the case with magnetic beads trapped in a standard capillary, thereby having less effect on the experimental conditions. Using numerical simulations and microscopic visualizations, the capture of beads inside a bubble cell was investigated with two magnet configurations. Pressure-driven and electro-osmotic flow velocities were measured for different amounts of protein-A-coated beads or C18-functionalized beads (RPC-18). Solid-phase extraction of a model antibody on protein-A beads and preconcentration of fluorescein on RPC-18 beads were performed as proof of concept experiments.     

An investigation of the stored energy and thermal stability in a Cu–Ni–Si alloy processed by high-pressure torsion

ABSTRACT

The stored energy and activation energy for recrystallization were investigated for a Cu-Ni-Si alloy after high-pressure torsion processing for N?=?½, 1, 5 and 10 turns at room temperature. The contributions of geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs) and vacancies to the stored energy were calculated through the Vickers microhardness measurements, kernel average misorientation (KAM) measurements and an analysis by differential scanning calorimetry (DSC). The results show that the total stored energy decreases rapidly after equivalent strain of ε_eq?～?9 and then saturates through ε_eq?～?86 at ～70 J/mol. Concurrently, the local stored energy in GNDs and SSDs was found to depend strongly on the radial distance from the centre of the disc and increase with increasing equivalent strain at ε_eq?～?16 and saturate with further straining. Accordingly, the results indicate that the GNDs and vacancies are responsible for the high stored energy in the initial stage of deformation at equivalent strain range of ε_eq?=?8.6–16 and thereafter their contribution decreases slightly due to the occurrence of dynamic recrystallization and the formation of fine grains. At the same time, the contribution of the SSDs is similar to that of the GNDs only in high strain deformation as at ε_eq?=?49.3 to accommodate the deformation process. An activation energy for recrystallization was estimated in the range of ～?89.7–98.7 kJ/mol, thereby suggesting poor thermal stability.     

Mathematical study of rotating fluids with resonant surface stress

We are interested here in describing the linear response of a highly rotating fluid to some surface stress tensor, which admits fast time oscillations and may be resonant with the Coriolis force. In addition to the usual Ekman layer, we exhibit another - much larger - boundary layer, and we prove that for large times, the effect of the surface stress may no longer be localized in the vicinity of the surface. From a mathematical point of view, the main novelty here is to introduce some systematic approach for the study of boundary effects.     

Anomalous diffusion of water in [BMIM][TFSI] room-temperature ionic liquid

We have studied the self-diffusion properties of butyl-methyl-imidazolium bis(trifluoromethylsulfonyl)-imide ([BMIM][TFSI]) + water system. The self-diffusion coefficients of cations, anions, and water molecules were determined by pulsed field gradient NMR. These measures were performed with increased water quantity up to saturation (from 0.3 to 30 mol %). Unexpected variations have been observed. The self-diffusion coefficient of every species increases with the quantity of water but not in the same order of magnitude. Whereas very similar evolutions are observed for the anion and cation, the increase is 25 times greater for water molecules. We interpret our data by the existence of phase separation at microscopic scale.