Effect of high voltage electrical discharges on filtration properties of Saccharomyces cerevisiae yeast suspensions

In the present work the dead-end filtration of Saccharomyces cerevisiae yeast suspensions disrupted by high voltage electrical discharges (HVED treatment) was investigated. The efficiency of disruption was evaluated using conductivity disintegration index of suspension Z (Z = 0–1) and absorbance spectra of supernatant solutions. The electronic microscopy study, particle sizing and measuring of ζ-potential and turbidity were used to characterize variation of the colloidal properties of a yeast suspension during disruption. The HVED treatment was found to cause an effective disruption of yeast cells and extraction of intracellular proteins and other bio-products. The study of filtration revealed suspension filterability deterioration after disruption. It was shown that filtration behaviour of the HVED-processed suspensions was governed by cake formation, the filtrate volume decreased and the cake resistance increased with increase of Z. For high levels of disruption (Z > 0.99), filtration was governed by membrane fouling. The optimal dosage of polycationic flocculant promoted the formation of flocks and accelerated filtration. However, selected flocculant (poly(diallyldimethylammonium chloride)) provoked binding of bio-product and was inappropriate for using as an agent enhancing extraction from disrupted yeast cells.     

The nature of active sites in high-silica zeolites containing platinum and cobalt nanoparticles

The calculations of interaction of Co₆ and Pt₆ nanoparticles with silicalite ZSM-5 and zeolite HZSM-5 were performed by the density functional theory method. Introduction of cobalt or platinum to silicalite slightly stabilizes the metal cluster and induces a small positive charge on the Co₆ particle and an appreciable negative charge on the Pt₆ particle. In the case of cobalt, the interaction of the metal particle with the acid zeolite is accompanied by a proton transfer from the Brønsted acid site to the surface of the metal cluster, resulting in the formation of a hydride-like structure, whereas in the Pt-zeolite system a complex cation containing adsorbed hydrogen atom is formed.     

Divergence of a thin elongated plate in supersonic gas flow

Buckled forms of a thin elastic flexible elongated plate lying on elastic base in supersonic gas flow are computed by bifurcation theory methods. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Methods of Bifurcation Theory in Multiparameter Problems of Hydroaeroelasticity

Applying bifurcation theory methods to nonlinear boundary value problems for ordinary differential equations (ODEs) of the fourth and higher orders encounters technical difficulties related to studying the spectrum of direct and adjoint linearized problems and constructing Green functions (i.e., proving the spectral problems to be Fredholm and determining the manifolds of bifurcation points). In order to overcome these difficulties, methods for separating the roots of relevant characteristic equations have been proposed, with the subsequent representation of the bifurcation manifolds in terms of these roots; this enables investigation of nonlinear problems in their rigorous statement. Such an approach is considered using the example of a two-point boundary value problem for a fourth-order ODE in which a statically bent pipeline section is described as a flexible elastic hollow rod, with a liquid flowing inside it, that is compressed or stretched by external boundary conditions with a free sliding left end and fixedly mounted right ends.     

Polarization spectroscopy of a conducting surface

A method of polarization spectroscopy for a conducting surface characterized by a high sensitivity to the state of the surface and its transition layer is proposed. The method uses excitation of surface electromagnetic waves (SEWs) by a linearly polarized probe beam incident on the surface under study and compensation for the phase shift between the p and s components arising upon the SEW excitation. The applicability and competitiveness of the method in both the visible and the IR range is established. The method is tested on an LEF-3M ellipsometer in the visible range by studying the oxidation process in an evaporated copper film.     

Interaction of Hafnium Chlorides with Magnesium,Aluminum, and Lead in Molten Alkali Metal Chlorides

The thermodynamic characteristics of the interaction of hafnium(II) and hafnium(IV) chlorides with magnesium, aluminum, and lead in molten alkali metal chlorides were calculated.     

Stacking reactions of the borole complex Cp*Rh(η5-C4H4BPh) with the dicationic fragments [Cp*M]2+ (M = Rh or Ir)

The reaction of the (borole)rhodium iodide complex [(η-C₄H₄BPh)RhI]₄ with Cp^*Li afforded the sandwich compound Cp^*Rh(η-C₄H₄BPh) (4). The reactions of compound 4 with the solvated complexes [Cp^*M(MeNO₂)₃]²⁺(BF ₄ ⁻ )₂ gave triple-decker cationic complexes with the central borole ligand [Cp^*Rh(η-η⁵:η⁵-C₄H₄BPh)MCp^*]²⁺(BF ₄ ⁻ )₂ (M = Rh (5) or Ir (7)). The structure of complex 4 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1525–1527, September, 2006.     

Extraction preconcentration with anionic surfactants in acidic solutions

Extraction preconcentration with anionic surfactants in acidic solutions on the basis of the cloud point was studied. Advantages and disadvantages of this method were considered. Conditions of the phase separation of some anionic surfactants (sodium decyl sulfate, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate) in acidic solutions were studied. With the example of pyrene and its derivatives, it was demonstrated that these surfactants can be used for extraction preconcentration. Analytical characteristics of the determination of pyrene and its derivatives in model aqueous solutions by the fluorimetric method in combination with extraction preconcentration with sodium dodecyl sulfate were obtained