Features of the composition and structural transformations of manganese minerals of the lake Bol’shoe Miassovo (South Ural)

The mineral and microelement composition of natural manganese minerals from iron-manganese concretions of the Bol’shoe Miassovo lake (South Ural) is investigated. The structural transformations of the samples under the effect of different temperatures are studied. Apart from layered 9.6 Å and 7.2 Å structures of manganese minerals the lake samples often contain various manganese-containing carbonates. For carbonate minerals by IR spectroscopy the dependence of the wavenumbers of ν₂ and ν₄ vibrations of the CO₃ group on the mineral composition is analyzed. The composition of macro- and microelements of iron-manganese concretions of Bol’shoe Miassovo lake varies in wide ranges not only in different samples, but also in different parts of the same sample. An analysis of the microstructure of lake manganese concretions revealed their biomorphic nature that is exhibited in globe-shaped to filament organic bacterial forms.     

Synthesis of New 4,4a-Dihydroxanthones via [4+2]-Cycloaddition Reaction

Russian Journal of General Chemistry - The effect of electronic properties of substituents in the reactants on the [4+2]-cycloaddition of 3-vinyl-chromen-4-ones (dienes) and N-vinylpyrrolidines...     

Natural and synthetic manganese minerals

The mineral and microelement composition and structures have been studied and a comparative analysis has been carried out for manganese minerals with the general formula [Mn(O,OH)₂]⁺[R_0.5–1(OH)_21.5] · nH₂O (R = Mn, Na, K, Ni, Co, Ca, and others) that built iron-manganese concretions raised from different areas of the Sea of Okhotsk and the Bering Sea, and their synthetic analogues. The structures of synthetic manganese species were found to better withstand temperature impacts than those of the native minerals studied under the same conditions.     

Structure and Magnetoresistance of Co–Gd and Al–Co–Gd Alloy Films

Technical Physics - Structural data and dependences of the film resistance on magnetic field strength R(H) are presented for Co–Gd and Al–Co–Gd alloy films obtained by vacuum...     

Modified Ceria-Zirconia Fluorite-Like Catalysts for the Combustion of Methane

For dispersed ceria-zirconia-based solid solutions prepared via the polymerized complex method and annealed at 700℃, effects of bulk doping by Ca, Mn, Co, Bi or Nb cations and surface modification by Mn and Pt on their structural features, surface/bulk oxygen reactivity and catalytic activity in methane combustion are considered. With up to 20 mol% doping, a structural type of homogeneous solid solutions of anion-deficient fluorite with disordered anion vacancies is formed. Doping by transition metal cations or Pt increases the mobility and reactivity of the surface/bulk oxygen. A broad variation in specific rates of methane combustion for the studied systems was observed, suggesting structural sensitivity of this reaction. In general, there is no universal relationship between the oxygen mobility, the reactivity and the catalytic activity in methane combustion, which is explained by the factor of specific methane activation on surface active sites. For the Pt-promoted samples, Pt efficiency in methane activation depends on the Pt-support interaction, and the most favorable ones being mixed Pt/MnOx and Pt/NbOx clusters on the surface of the supports that exhibit high lattice oxygen mobilities.     

Dynamical behavior and network analysis of an extended Hindmarsh–Rose neuron model

Nonlinear Dynamics - In this paper, the extended Hindmarsh–Rose neuron model, which considers the slow intracellular exchange of calcium ions between its store and the cytoplasm, is studied....