Adaptive iterative regularization schemes for two‐dimensional integral‐algebraic systems

The main idea of this paper is to utilize the adaptive iterative schemes based on regularization techniques for moderately ill‐posed problems that are obtained by a system of linear two‐dimensional Volterra integral equations with a singular matrix in the leading part. These problems may arise in the modeling of certain heat conduction processes as well as in the dynamic simulation packages such as compressible flow through a plant piping network. Owing to the ill‐posed nature of the first kind Volterra equation that appears in the system, we will focus on the two families of regularization algorithms, ie, the Landweber and Lavrentiev type methods, where we treat both the exact and perturbed data. Our aim is to work directly with the original Volterra equations without any kind of reduction. Two fast iterative algorithms with reasonable computational complexity are developed. Numerical experiments on a few test problems are used to illustrate the validity and efficiency of the proposed iterative methods in comparison with the classical regularization methods.     

M?ssbauer study of dissimilatory reduction of iron contained in glauconite by alkaliphilic bacteria

⁵⁷Fe M?ssbauer investigations of glauconite and new solid phases formed during the process of the bacterial growth in alkaline environment were carried out at room temperature, 78 K and 4.8 K. The magnetically ordered phase formed during bioleaching of glauconite by G. ferrihydriticus in pure culture or in combination with Cl. alkalicellulosi represented as a mixture of off-stoichiometric magnetite and maghemite. In case of combined binary bacterium culture growth the relative content of magnetically ordered phase was more than for the G. ferrihydriticus growth.     

Differential-algebraic equations with a small nonlinear term

In the present paper, we generalize some known results of the theory of differentialalgebraic equations to a more complicated case under the assumption that the nonlinear term is small. We give an asymptotic estimate of the behavior of the solution with respect to the parameter μ.     

Mössbauer study of bacterial iron-reduction processes in natural glauconite and biotite

Interaction between a bacterial monoculture of alkaliphylic G. ferrihydriticus along with binary cultures of G. ferrihydriticus and cellulolytic C. alkalicellulosi and natural biotite and glauconite under alkaliphylic conditions is investigated by means of Mössbauer spectroscopy. Measurements were performed over a range of temperatures from T = 4.8 K to T = 300 K. It was found that a new magnetically ordered phase was formed during culture growth. This new phase was a mixture of nonstoichiometric magnetite and maghemite. The relative amount of the magnetically ordered phase in the monoculture of G. ferrihydriticus when interacting with glauconite is less than in the case of the binary culture. Iron reduction glauconite is also more intense than in biotite.     

Polysaccharide from the leaves ofPhytolacca americana

A polysaccharide has been isolated from the leaves ofPhytolacca americana and has been characterized. It has been established that it contains residues of galactose, arabinose, xylose, and rhamnose, in a ratio of 3:4:1:3 and also D-galacturonic acid (85–90%). The results obtained permit the polysaccharide to be assigned to the class of pectin substances.     

Mössbauer spectroscopy in studying magnetite formed by iron- and sulfate-reducing bacteria

The kinetics of iron mineral formation by thermophilic dissimilatory iron reducing bacteria using Fe(III) amorphous hydroxide and acetate CH₃COO^? as an electron acceptor and donor, respectively, was investigated by Mössbauer spectroscopy. The effects of various physical and chemical conditions and the presence of an inert organic substance on the formation of biogenic minerals were considered. The production of magnetite due to microbial sulfate reduction by hyperthermophilic dissimilatory sulfate-reducing microorganisms was investigated by Mössbauer spectroscopy methods.