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A S Dukhin

Publications and source records attributed to A S Dukhin.

7 recordsLinked to original sources
PubMed2005

Use of ultrasound for characterizing dairy products.

It has been known for a long time that acoustic measurements offer some unique features for characterizing liquid food products in their intact state, without any preparation or destruction of the product sample. Acoustic characterization can yield information about fat content, droplet size distribution, and kinetics of product variation with time. Furthermore, acoustic methods are very attractive for on-line process control. This paper addresses several questions: Why does ultrasound attenuate when propagating through a heterogeneous system? What properties of dairy products can be extracted from such ultrasound measurements? Which measurement is better for product characterization: attenuation or sound speed? What measurement precision is required to adequately characterize product properties? What frequency range is of most value for determining these product properties?It is possible to provide answers to many of these questions using experimental data, thereby avoiding, for the moment, any complex mathematical analysis. We present several applications of acoustic spectroscopy for characterizing dairy products, including characterization of the fat content in a wide variety of dairy products; calculation of the fat droplet size distribution in milk without dilution; and calculation of water droplet size in butter, without dilution or melting.

Acoustics↗
PubMed2004

Electroacoustic theory for concentrated colloids with overlapped DLs at arbitrary kappa alpha. I. Application to nanocolloids and nonaqueous colloids.

Existing theories of electroacoustic phenomena in concentrated colloids neglect the possibility of double layer overlap and are valid mostly for the "thin double layer," when the double layer thickness is much less than the particle size. In this paper we present a new electroacoustic theory which removes this restriction. This would make this new theory applicable to characterizing a variety of aqueous nanocolloids and of nonaqueous dispersions. There are two versions of the theory leading to the analytical solutions. The first version corresponds to strongly overlapped diffuse layers (so-called quasi-homogeneous model). It yields a simple analytical formula for colloid vibration current (CVI), which is valid for arbitrary ultrasound frequency, but for restricted kappa alpha range. This version of the theory, as well the Smoluchowski theory for microelectrophoresis, is independent of particle shape and polydispersity. This makes it very attractive for practical use, with the hope that it might be as useful as classical Smoluchowski theory. In order to determine the kappa alpha range of the quasi-homogeneous model validity we develop the second version that limits ultrasound frequency, but applies no restriction on kappa alpha. The ultrasound frequency should substantially exceed the Maxwell-Wagner relaxation frequency. This limitation makes active conductivity related current negligible compared to the passive dielectric displacement current. It is possible to derive an expression for CVI in the concentrated dispersion as formulae inhering definite integrals with integrands depending on equilibrium potential distribution. This second version allowed us to estimate the ranges of the applicability of the first, quasi-homogeneous version. It turns out that the quasi-homogeneous model works for kappa alpha values up to almost 1. For instance, at volume fraction 30%, the highest kappa alpha limit of the quasi-homogeneous model is 0.65. Therefore, this version of the electroacoustic theory is valid for almost all nonaqueous dispersions and a wide variety of nanocolloids, especially with sizes under 100 nm.

Journal Article↗
PubMed2001

Acoustic and electroacoustic spectroscopy for characterizing concentrated dispersions and emulsions.

We describe two different techniques (acoustics and electroacoustics), both of which employ ultrasound instead of light for extracting information about the properties of liquid-based dispersions. Ultrasound can propagate through samples that are not transparent for light, which open up many new applications not possible with classical light scattering methods. Acoustic and electroacoustic techniques offer a unique opportunity to characterize concentrated dispersion, emulsions and microemulsions in their natural states. Elimination of a dilution step required for most other techniques (light scattering, sedimentation, electrophoresis) is crucial for an adequate characterization of liquid dispersions, especially when the high concentration leads to structured systems. As with any macroscopic method, ultrasonic techniques characterize the sample in two steps. The first step is to measure some macroscopic property. The second step involves some theoretical treatment of the measured raw data which yields the desired information. Acoustic spectroscopy deals with measuring the attenuation of ultrasound within a certain frequency range. Electroacoustic spectroscopy has two implementations depending on the driving force. We emphasize here on the so-called Colloid Vibration Current (CVI) which is generated by the sound wave as it passes through the dispersion. A review of the theoretical basis of acoustics and electroacoustics is given, with emphasis on models that have been applied to concentrated systems. Recently, new theories have been developed for both acoustics and electroacoustics using a 'coupled phase model' and 'cell model concept'. The coupled phase model is widely used for describing a relative motion of the particles and liquid in the sound wave. The cell model approach opens the way to include both particle-particle interactions and polydispersity into the theoretical model. Experimental evidence is presented that shows that this new approach is successful in concentrated systems up to 45% vol. A short review of the possible applications of acoustics and electroacoustics measurements to a range of systems is presented including: ceramics, mixed dispersed systems, chemical-mechanical polishing abrasives, emulsions, microemulsions and latex materials.

Acoustics↗
PubMed1992

Interaction of energized bacteria cells with particles of colloidal gold: peculiarities and kinetic model of the process.

It is found that the cells of Bacillus cereus B-4368 at energized state can concentrate the colloidal gold particles on their surface. It is shown that the process depends on metabolic reactions proceeding on the plasma membrane. The inhibitory analysis permits to suppose that the metal concentration is due to the functioning of ATP-dependent generator of the transmembrane potential, apparently, of proton ATPase. Kinetic characteristics of the process show the presence of an intermediate state in the formation of biomineral aggregates. A kinetic model of the studied process is suggested which describes the experimental data well.

Adenosine Triphosphatases↗
PubMed1992

Some problems of zeta potential determination in electrophoretic measurements on lipid membranes.

Electrophoretic mobilities were measured for cardiolipin, phosphatidylinositol and phosphatidylserine liposomes in solutions of potassium chloride. The zeta potential as a function of ionic strength deviates significantly from the predictions of the double-layer theory in the 10(-3)-5.10(-2) M range. This might be due to changes in pH in the course of the experiment and/or to the inapplicability of the Smoluchowski equation at low ionic strengths. Taking into account the relaxation effects results in theoretical curves, calculated for various particle sizes at low ionic strength, which are in better agreement with the experiment. However, for quantitative comparison with experimental data, further investigations are necessary.

Cardiolipins↗