Metal sorption by biomass of melanin‐producing fungi grown in clay‐containing medium

The sorption of toxic metals by fungal mycelia grown in clay‐containing medium is reported in this work. Biomass of melanin‐producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay‐containing medium were compared for their equilibrium Cu and Cd uptake from pH‐buffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal‐binding ability of the fungal–clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Q_max) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay‐containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the ‘biomineral’ association. © 2002 Society of Chemical Industry     

Crack propagation in ceramic composites with layered granular structure

Fracture experiments under conditions of subcritical crack extension were performed with double torsion and single-edge notched bend specimens of different alumina-based ceramic composites having layered granular structure. It is shown that it is possible to increase significantly the work-of-fracture as a result of layered granular structure organization. The pecularities of structure influence on the crack propagation kinetics were investigated, and the possibilities of acceleration and deceleration of subcritical crack growth are reported.     

Equivalence of the probability measures generated by the solutions of nonlinear evolution differential equations in a Hilbert space, disturbed by Gaussian processes. Part II

The paper continues the studies in the equivalence of the measures generated by the solutions of nonlinear evolution differential equations with unbounded linear operators perturbed by random Gaussian processes in a Hilbert space, in particular í. Two different nonlinear evolution differential equations perturbed by the same random Gaussian process in the right-hand side are considered in the space í. The sufficient existence and uniqueness conditions are established for the solutions of these equations, the equivalence of the measures generated by the solutions is proved, and explicit formulas for the Radon–Nikodym density of the respective measures calculated in terms of the coefficients of the considered equations are written.     

Composite ceramic materials with SiC fiber

The technology and mechanical characteristics of composite ceramic materials strengthened by discrete and continuous fibers of silicon carbide are described. The introduction of an 8% volume fraction of continuous SiC fibers into cordierite increases its strength by almost a factor of 2. Among composites strengthened by SiC whisker the highest density is exhibited by materials with a matrix of Al₂O₃ - ZrO₂ (580 MPa). Materials with matrices of Al₂O₃ and synthetic mullite have mean ultimate bending strengths of 460 and 420 MPa, respectively. The microstructures of the materials are described.Translated from Ogneupory, No. 8, pp. 3 – 6, August, 1995.     

Absorbing Elements Based on a Uniform Resistive Film for the Implementation of a Wide Range of Radio Signal Power Attenuations

Russian Microelectronics - Rectangular and complex-shaped absorbing elements based on a uniform resistive film are used for constructing waveguide, coaxial, and microstrip attenuators. A decrease...     

Inductive inference and argumentation methods in modern intelligent decision support systems

Improvement of the classification quality for the generalization problem is considered. In order to improve the classification models produced by generalization algorithms, it is proposed to use argumentation methods based on defeasible reasoning with justification degrees. New methods and algorithms are proposed, and experimental results on various test data sets are described, including instances with noisy initial data.     

Functionalized polyglycidol-CuCl-complexes as catalysts in the oxidative coupling reaction of terminal acetylenes

Summary Novel hyperbranched amino-terminated polyglycidoles have been synthesized and tested as macromolecular ligands in the oxidative coupling reaction of phenylacetylene. Amino-terminated polyglycidoles-CuCl complexes showed to be more effective catalysts than the reference monomeric tertiary amines-CuCl ones, but less effective than the most efficient N,N,N'N'-tetramethylethylenediamine-(TMDA) CuCl complex. The difference in performance of monomeric and hyperbranched ligands is probably due to two factors. The first one is better complexation abilities and the second is the local increase of reagent concentration. Received: 28 April 2001/Revised version: 29 August 2001/Accepted: 5 September 2001     

Deformations of Working Elements in Oil Free Scroll Vacuum Pumps

The mechanical and thermal causes of deformations of the orbiting and the fixed elements of oil free vacuum pumps are considered. Basic data for deformation calculation are geometric dimensions of the pump and dependence of working chamber volume on the orbiting scroll element rotation angle. Gas temperature and pressure values in each vacuum pump chamber are obtained with the help of a working process mathematical model. Deformation calculation is carried out by the finite element method realized in the software ANSYS. It is shown that deformations caused by pressure‐induced mechanical forces do not have considerable influence on the change of radial clearances between the scrolls. They may not be taken into account for pumping characteristics calculation. Thermal‐induced deformations are much greater, and the change of the clearances due to this cause may be 25 % and even larger.