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Pimienta V.,Toulouse 1 University Capitole | Brost M.,Toulouse 1 University Capitole | Kovalchuk N.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Bresch S.,Florida State University | Steinbock O.,Florida State University
Angewandte Chemie - International Edition | Year: 2011

Generation of cohesive motion was observed during the dissolution of mm-sized drops of dicholoromethane into aqueous surfactant solutions. This system shows pulsating drops, multi-armed rotors, and polygonal shapes. The sharp tips of these patterns eject much smaller droplets to form expanding halos or swirling chains. The daughter droplets also undergo cascades of secondary and higher-order splitting events. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ravera F.,CNR Institute of Neuroscience | Loglio G.,University of Florence | Kovalchuk V.I.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry
Current Opinion in Colloid and Interface Science | Year: 2010

Dilational rheology represents a powerful tool to investigate equilibrium and dynamic properties of simple and more complex interfacial layers containing surfactants, proteins, polymers or micro-nano sized particles. Concerning the experimental techniques for dilational rheology, drop/bubble tensiometers based on the acquisition of the drop/bubble profile and capillary pressure tensiometers are especially effective.This article focuses on oscillating drop/bubble methodologies where harmonic variations of the interfacial area are utilized for the measurement of the dilational viscoelasticity in the frequency domain. The increasing efficiency of these techniques of the last ten years is due, from one side, to the implementation of advanced instrumentations which make faster the drop/bubble control and the data acquisition and, on the other side, to the application of new theoretical approaches for data acquisition and interpretation.A critical analysis of such drop/bubble instruments is presented where their potentialities and limitations are underlined. Moreover, recent improvements in the definition of calculation methods based on the modelling of the experimental set up are reviewed together with some examples of experimental studies based on the utilisation of such methodologies. © 2010 Elsevier Ltd.

Kovalchuk N.M.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Kovalchuk N.M.,Max Planck Institute of Colloids and Interfaces | Starov V.M.,Loughborough University
Advances in Colloid and Interface Science | Year: 2012

The forces acting in colloidal suspensions and affecting their stability and aggregation kinetics are considered. The approximations used for these forces in numerical simulations and the importance of the balanced account for both colloidal forces and hydrodynamic interactions are discussed. As an example the results of direct numerical simulations of kinetics of aggregation either with account for hydrodynamic interaction between particles or without it are compared by varying the parameters of the interaction potential between particles and fraction of solid. Simulations are based on the Langevin equations with pairwise interaction between particles and take into account Brownian, hydrodynamic and colloidal forces. It is confirmed that the neglecting of hydrodynamic interaction results in an accelerated growth of aggregates. The results of numerical simulations of aggregation kinetics are compared with well known analytical solutions. © 2011 Elsevier B.V.

Kovalchuk N.M.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Vollhardt D.,Max Planck Institute of Colloids and Interfaces
Langmuir | Year: 2010

Spontaneous nonlinear oscillations of surface tension produced by transfer of either octanoic or nonanoic acids from a droplet situated in the bulk water to the air/water interface are studied experimentally. It is shown that the oscillation amplitude decreases significantly with the increase of pH of aqueous phase. At pH > 6.5, detectable oscillations for the two fatty acids studied do not exist. The results are discussed in terms of the mechanism proposed recently for spontaneous oscillations produced by transfer of nonionic surfactants. © 2010 American Chemical Society.

Kovalchuk N.M.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Kovalchuk N.M.,Max Planck Institute of Colloids and Interfaces
Central European Journal of Chemistry | Year: 2012

Systems far from equilibrium are able to self-organize and often demonstrate the formation of a large variety of dissipative structures. In systems with free liquid interfaces, self-organization is frequently associated with Marangoni instability. The development of solutal Marangoni instability can have specific features depending on the properties of adsorbed surfactant monolayer. Here we discuss a general approach to describe solutal Marangoni instability and review in details the recent experimental and theoretical results for a system where the specific properties of adsorbed layers are crucial for the observed dynamic regimes. In this system, Marangoni instability is a result of surfactant transfer from a small droplet located in the bulk of water to air/water interface. Various dynamic regimes, such as quasi-steady convection with a monotonous decrease of surface tension, spontaneous oscillations of surface tension, or their combination, are predicted by numerical simulations and observed experimentally. The particular dynamic regime and oscillation characteristics depend on the surfactant properties and the system aspect ratio. © Versita Sp. z o.o.

Dukhin A.S.,Dispersion Technology Inc. | Ulberg Z.R.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Karamushka V.I.,University of Educational Management | Gruzina T.G.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry
Advances in Colloid and Interface Science | Year: 2010

Experimental evidence collected more than 20 years ago in different laboratories suggests that the interactions between live biological cells and micro- and nanoparticles depend on their metabolic state. These experiments were conducted by reputable groups, led by prominent leaders such as H. Pohl of the USA, who was the inventor of dielectrophoresis, and B. Derjaguin of the Soviet Union who was the leading author of DLVO theory. The experiments had been mostly conducted with microparticles in the early 1980s. In the early 1990s, Ukrainian researchers showed that the interaction of live cells with gold nanoparticles consisted of an initial reversible step that also depended on cell metabolism. They found indirect evidence that the ion pumps of the cells were responsible for the reversible step. Ion pumps generate a transmembrane potential, a measurable and widely-used characteristic of the cell's energetic state. The transmembrane potential, in turn, strongly affects the ζ-potential, as was experimentally discovered 40 years ago by several independent groups using cell electrophoresis. This relationship should be taken into account when DLVO theory is considered as the basis for describing the interactions between live cells and micro- and nanoparticles. Unfortunately, detail theoretical analysis indicates that such modification would not be sufficient for explaining observed peculiarities mentioned above. That is why distinguished theoreticians such as Pohl, Frohlich, Derjaguin and others have suggested three theoretical models, presumably to explain these experiments. These theoretical models should be considered to be complementary to the well-established concepts developed on this subject in the molecular biology of cells and cell adhesion. This paper is not a revision of the existing models. It is an overview of the old and forgotten experimental data and discussion of the suggested theoretical models. The unusual interaction mechanisms are only specific for live biological cells and serve a dual role: either as a first barrier to protect the cell from potentially damaging, dispersed particulates, or as a means of accumulating useful substances. Both functions are critical for the modern problem of nanotoxicology. © 2010 Elsevier B.V. All rights reserved.

Dukhin A.S.,Dispersion Technology Inc. | Shilov V.N.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry
Journal of Colloid and Interface Science | Year: 2010

Propagation of ultrasound waves through a porous body saturated with liquid generates an electric response. This electroacoustic effect is called the " seismoelectric current" ; the reverse phenomenon, where an electric field is the driving force, is known as the " electroseismic current" The seismoelectric current can be measured with existing electroacoustic devices that were originally designed to characterize liquid dispersions. The versatility of electroacoustic devices allows them to be calibrated using dispersions and then applied to the characterization of porous bodies. Here, we present the theory of the seismoelectric effect, which we derived by following the path suggested 65. years ago by Frenkel. To verify this theory, we measured the seismoelectric current generated by sediments of micrometer-sized silica particles. We demonstrated that the measurement allowed the determination of porosity of the sediment and the calculation of the ζ-potential. The ζ-potential value, calculated using the suggested theory, closely agreed with the value independently measured for moderately concentrated dispersions using a well-known electroacoustic theory for dispersions. Measurements of the seismoelectric effect with existing electroacoustic probes open up new ways for characterizing the porosity and ζ-potential of porous bodies, including ones with low permeability. © 2010 Elsevier Inc.

Kovalchuk N.M.,Loughborough University | Kovalchuk N.M.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Trybala A.,Loughborough University | Starov V.M.,Loughborough University
Current Opinion in Colloid and Interface Science | Year: 2014

Recent developments in the studies of evaporation of liquid droplets placed on a solid substrate are reviewed for the droplet size typically larger than 1. μm, so that kinetics effects of evaporation are neglected. The attention is paid to the limits of applicability of classical diffusion model of evaporation, effect of substrate, evaporation of complex fluids and applicability for its description of the theory developed for pure liquids, and hydrothermal waves accompanying evaporation. © 2014.

Rulyov N.N.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry
Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy | Year: 2016

A theory of combined microflotation is proposed which reasonably accurately describes the kinetics of fine particles flotation utilising small quantities of fine bubbles in combination with the coarse bubbles. The theory has been applied to analyse the experimental findings of fine quartz flotation by the method of combined microflotation. The theory predicts the capture efficiency of particles and fine bubbles by the coarse bubbles and the efficiency of hetero-aggregation of particles and fine bubbles in the non-uniform hydrodynamic field of a flotation cell. It is shown that the optimal size of the fine bubbles increases approximately linearly with increase of the size of particles and diameter of the coarse bubbles; the dependence on the size of particles is stronger than on the diameter of the coarse bubbles. A theoretical explanation is offered for the linear dependence of the combined microflotation rate constant on the volume dosage of fine bubbles per weight unit of solids. © 2016 Institute of Materials, Minerals and Mining and The AusIMM.

Samchenko Y.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Ulberg Z.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Korotych O.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry
Advances in Colloid and Interface Science | Year: 2011

This paper represents the review of the last investigations in the field of smart polymeric hydrogels and our contribution to this matter. New hydrogel systems and nanocomposites based on acrylic monomers (acrylamide, acrylonitrile, acrylic acid, N-isopropylacrylamide etc.) with incorporated nanosized colloidal silver, hydroxyapatite and carbon nanotubes with a new set of properties have been obtained and examined. These systems can sharply change their characteristics when minor external physical (electric and magnetic fields, temperature etc.) or chemical (pH, ionic strength) stimuli are applied. Such stimulus-responsive polymeric systems are very promising from the standpoint of different medical applications, especially for the development of intelligent drug delivery systems. On the base of designed hydrogel iontophoretic transdermal therapeutic systems, endoprosthesis for the replacement of bone tissue and hydrogel burns coatings with immobilized mesenchymal cells were obtained and tested. © 2011 Elsevier B.V. All rights reserved.

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