Search results for "Mesoscopic physics"
showing 10 items of 122 documents
Hierarchical Structuring in Block Copolymer Nanocomposites through Two Phase-Separation Processes Operating on Different Time Scales
2013
Tailoring the size and surface chemistry of nanoparticles allows one to control their position in a block copolymer, but this is usually limited to one-dimensional distribution across domains. Here, the hierarchical assembly of poly(ethylene oxide)-stabilized gold nanoparticles (Au-PEO) into hexagonally packed clusters inside mesostructured ultrathin films of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is described. A close examination of the structural evolution at different nanoparticle filling fractions and PEO ligand molecular weights suggests that the mechanism leading to this structure-within-structure is the existence of two phase separation processes operating on differe…
Micro- and mesoscopic process interactions in protein coagulation
2000
It has recently been recognized that pathological protein coagulation is responsible for lethal pathologies as diverse as amyloidosis, Alzheimer and TSE. Understanding the coagulation mechanisms is therefore stirring great interest. In previous studies we have shown that on profoundly different systems coagulation is the result of a strong interaction between two processes on different length scales (mesoscopic and microscopic). Here we report experiments on bovine serum albumin (BSA) showing that the overall mechanism is the result of at least 3 distinct and strongly intertwined processes, on both length scales: molecular conformational changes, solution demixing and intermolecular crossli…
A mesoscopic approach to radiation-induced defect aggregation in alkali halides stimulated by the elastic interaction of mobile Frenkel defects
1994
The radiation-induced aggregation of Frenkel defects in alkali halides is studied in terms of a mesoscopic approach. The asymmetry in elastic interactions between mobile interstitials (I–I) and bet...
Joint reality and Bell inequalities for consecutive measurements
2006
Some new Bell inequalities for consecutive measurements are deduced under joint realism assumption, using some perfect correlation property. No locality condition is needed. When the measured system is a macroscopic system, joint realism assumption substitutes the non-invasive hypothesis advantageously, provided that the system satisfies the perfect correlation property. The new inequalities are violated quantically. This violation can be expected to be more severe than in the case of precedent temporal Bell inequalities. Some microscopic and mesoscopic situations, in which the new inequalities could be tested, are roughly considered.
Emerging Evidences of Mesoscopic-Scale Complexity in Neat Ionic Liquids and Their Mixtures
2017
Ionic liquids (ILs) represent a blooming class of continuously developing advanced materials, with the aiming of a green chemical industry. Their appealing physical and chemical properties are largely influenced by their micro- and mesoscopic structure that is known to possess a high degree of hierarchical organization. High-impact application fields are largely affected by the complex morphology of neat ionic liquids and their mixtures. This Perspective highlights new arising research directions that point to an enhanced level of structural complexity in several IL-based systems, including mixtures. The latter represent a change in paradigm in the approach to formulate new, task-specific I…
Pressure-responsive mesoscopic structures in room temperature ionic liquids
2015
Among the most spectacular peculiarities of room temperature ionic liquids, their mesoscopically segregated structural organization keeps on attracting attention, due to its major consequences for the bulk macroscopic properties. Herein we use molecular dynamics simulations to explore the nm-scale architecture in 1-octyl-3-methylimidazolium tetrafluoroborate, as a function of pressure. This study reveals an intriguing new feature: the mesoscopic segregation in ionic liquids is characterized by a high level of pressure-responsiveness, which progressively vanishes upon application of high enough pressure. These results are in agreement with recent X-ray scattering data and are interpreted in …
Polymer solutions: Equilibrium clusters versus shear clusters
2021
Abstract Polymer solutions are inhomogeneous on mesoscopic scales as a result of chemical bonds linking their monomeric units. This situation leads to polymer clusters within which the polymer concentration c cluster is only a small fraction of the overall concentration c. The ratio c/ c cluster (overlap parameters Ω ) quantifies the number of clusters that need to overlap to yield c. Equilibrium clusters (minimization of Gibbs energy) and shear clusters (minimization of entropy production) differ fundamentally where Ω equil ≥ Ω shear . Only in the vicinity of the glass transition temperature and at high concentration the opposite is the case. Experimental information on Ω equil as a functi…
Nonequilibrium depletion interactions in active microrheology.
2017
Entropic depletion forces arise between mesoscopic bodies that are immersed in a suspension of macromolecules, such as colloid-polymer mixtures. Here we consider the case of a driven colloidal probe in the presence of another, passive colloidal particle, both solvated in an ideal bath of small spherical particles. We calculate the nonequilibrium forces mediated by the depletants on the two colloidal particles within a dynamical superposition approximation (DSA) scheme. In order to assess the quality of this approximation, and to obtain the colloidal microstructure around the driven probe, we corroborate our theoretical results with Brownian dynamics simulations.
Interaction of Heparins and Dextran Sulfates with a Mesoscopic Protein Nanopore
2009
A mechanism of how polyanions influence the channel formed by Staphylococcus aureus alpha-hemolysin is described. We demonstrate that the probability of several types of polyanions to block the ion channel depends on the presence of divalent cations and the polyanion molecular weight and concentration. For heparins, a 10-fold increase in molecular weight decreases the half-maximal inhibitory concentration, IC(50), nearly 10(4)-fold. Dextran sulfates were less effective at blocking the channel. The polyanions are significantly more effective at reducing the conductance when added to the trans side of this channel. Lastly, the effectiveness of heparins on the channel conductance correlated wi…
CH of masonry materials via meshless meso-modeling
2014
In the present study a multi-scale computational strategy for the analysis of masonry structures is presented. The structural macroscopic behaviour is obtained making use of the Computational Homogenization (CH) technique based on the solution of the boundary value problem (BVP) of a detailed Unit Cell (UC) chosen at the meso-scale and representative of the heterogeneous material. The smallest UC is composed by a brick and half of its surrounding joints, the former assumed to behave elastically while the latter considered with an elastoplastic softening response. The governing equations at the macroscopic level are formulated in the framework of finite element method while the Meshless Meth…