Mössbauer study of iron minerals transformations by <Emphasis Type="Italic">Fuchsiella ferrireducens</Emphasis>

Biogenic transformations of iron-containing minerals synthesized ferrihydrite, magnetite and hydrothermal siderite by anaerobic alkaliphilic bacterium Fuchsiella ferrireducens (strain Z-7101^T) were studied by ⁵⁷Fe Mössbauer spectroscopy. Mössbauer investigations of solid phase samples obtained after microbial transformation were carried out at room temperature and at 82 K. It was found that all tested minerals transformed during bacterial growth. In the presence of synthesized ferrihydrite, added as an electron acceptor, a mixture of large (more than 100 nm) and small (～5 nm) particles of magnetically ordered phase and siderite was formed. Synthesized magnetite that contains both Fe³⁺ and Fe²⁺ forms could serve as electron acceptor as well as an electron donor for F.ferrireducens growth. As a result of its biotransformation, no siderite formation was observed while small particles of magnetite were formed. In the case of the addition of siderite as an electron donor formation of a small amount of a new phase containing Fe²⁺ caused by recrystallization of siderite during bacterial growth was detected.     

Mössbauer investigations of natural and synthetic tochilinite and valleriite

Samples of natural and synthetic tochilinites and valleriites were investigated by Mössbauer spectroscopy. Synthesis of tochilinite was carried out at different temperatures and Fe/Mg ratio in the initial mixture. The relative amounts of obtained phases as functions of Mg atom relative content in the initial mixture were derived. It was shown that Mg atoms preferred to occupy one of two nonequivalent positions in brucite-like layers when entering the tochilinite structure. Parameters of hyperfine interaction were determined for valleriite and crystal chemical identification of ⁵⁷Fe subspectra was carried out.     

Nonparametric estimators in models of incomplete repair

In this paper, an incompletely repairable model using the concept of virtual age of an element is presented. Translated fromStatisticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 69–77, Perm, 1993.     

Absorption of pulsed CO2 laser radiation by air and carbon dioxide

An optoacoustical method is used in experimental study of nonlinearity in absorption of pulsed CO₂ laser radiation by air with CO₂ and H₂O added and pure CO₂. The laser pulse consists of frequencies related to several rotational transitions, generated simultaneously. Nonlinearity in absorption was detected for laser radiation levels above 0.2 MW/cm².Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 49–51, October, 1982.