X-ray Study of Iron-containing Derivatives of Arabinogalactan

Iron-containing derivatives of arabinogalactan (ferroarabinogalactans) were subjected to X-ray diffraction analysis to determine the form and structure of bound iron. Crystal lattice parameters a of the iron-containing phase were measured and the average crystallite size was determined.     

Redox reactions of arabinogalactan with silver ions and formation of nanocomposites

Formation of silver nanoparticles in the course of chemical reduction of AgNO₃ with arabinogalactan in aqueous alkaline solution was studied by electronic absorption spectroscopy and X-ray diffraction analysis. The pH of the solution was found to be the major factor affecting the degree of reduction of Ag⁺ ions. The probable reaction mechanism was discussed. Composites containing up to 58% Ag, with the metal particle size of 7–16 nm, were prepared. The nanoparticle size can be controlled by varying the reactant ratio AgNO₃: arabinogalactan. Chemical modification of arabinogalactan was confirmed by IR and ¹³C NMR spectroscopy and by TLC.     

Dynamic interactive stabilization of systems of flow with processor sharing

An interactive protocol for the control for a switched system of flow with process sharing is proposed. It is shown that the protocol suggested generates the required periodic process as a global attractor.     

Structures and regimes of shear flow in a plane cavity with translating boundaries

Stability of shear flow in a plane cavity whose boundaries translate in opposite directions is analyzed by solving the nonstationary Navier-Stokes equations numerically. It is shown that, depending on the Reynolds number and the cavity aspect ratioH/R, there may exist either a single-vortex, or a multi-eddy, or an intermediate flow regime with a bridge, all of which are stable. No oscillatory regime was found forH/L=0.1–10 and Re=1–3000.Nizhnii Novgorod, Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 53–56, March–April, 1995.     

Dynamic interactive stabilization of the switching Kumar-Seidman system

A dynamic control protocol for the Kumar-Seidman flexible production system represented in general algebraic form is suggested. The ultimate purpose of the study is to minimize the total amount of work per unit time. The suggested protocol is proved to generate the required periodic process as a global attractor. In order to substantiate convergence, a number of statements of classical Frobenius-Perron theory are generalized to monotone piecewise affine nonlinear operators. A new method for exciting the required production cycles in the spirit of classical Poincaré’s method is suggested. The approach is based on a new stability criterion for an equilibrium of a discrete stationary system. A dynamic control protocol for the Kumar-Seidman flexible production system represented in general algebraic form is suggested and proved to generate the required periodic process as a global attractor. In order to substantiate convergence, a number of statements of classical Frobenius-Perron theory are generalized to monotone piecewise affine nonlinear operators.     

Microporous Polymeric 3D Scaffolds Templated by the Layer‐by‐Layer Self‐Assembly

Polymeric scaffolds serve as valuable supports for biological cells since they offer essential features for guiding cellular organization and tissue development. The main challenges for scaffold fabrication are i) to tune an internal structure and ii) to load bio‐molecules such as growth factors and control their local concentration and distribution. Here, a new approach for the design of hollow polymeric scaffolds using porous CaCO₃ particles (cores) as templates is presented. The cores packed into a microfluidic channel are coated with polymers employing the layer‐by‐layer (LbL) technique. Subsequent core elimination at mild conditions results in formation of the scaffold composed of interconnected hollow polymer microspheres. The size of the cores determines the feature dimensions and, as a consequence, governs cellular adhesion: for 3T3 fibroblasts an optimal microsphere size is 12 μm. By making use of the carrier properties of the porous CaCO₃ cores, the microspheres are loaded with BSA as a model protein. The scaffolds developed here may also be well suited for the localized release of bio‐molecules using external triggers such as IR‐light.

     

Synthesis and adsorption properties of zeolite-like aluminophosphates

Zeolite-like aluminophosphates AlPO₄-5, AlPO₄-18, and AlPO₄-20, were prepared in conditions which differ from those described in the literature. The adsorption isotherms of H₂O, CH₃OH, n-C₄H₉OH, and i-C₄H₄₉OH at 18°C and Ar at –196°C were investigated. The observed molecular-sieve effect is in agreement with the concepts on the structure of these aluminophosphates. An unusual shape of the water adsorption isotherms was observed. Similarities were observed in the isobaric absorption of water molecules by crystal hydrates and the zeolite-like aluminophosphates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2409–2414, November, 1989.     

Thermochemistry of AII(VUO6)2 · nH2O Compounds (AII = Mn, Fe, Co, Ni, Cu, Zn, Cd)

Standard enthalpies of formation of uranovanadates of 3(4)d transition metals at 298.15 K were determined. The isobaric heat capacity of Co(VUO₆)₂ · 4H₂O was measured. The standard Gibbs functions of formation of the compounds were calculated on the basis of these data using approximate methods of absolute entropy calculation. The thermochemical characteristics of the synthesis and dehydration of uranovanadates were considered.