Molecular structure of σ3λ5

Institute for Organic Chemistry, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 117–128, September–October, 1991.     

Some metric properties of p-adic numbers

Siberian Mathematical Journal -     

Microwave assisted synthesis of hydroxyapatite nano strips

Synthesis of hydroxyapatite (HAP) nano strips was carried out by chemical precipitation method followed by microwave irradiation. The microwave assisted reactions proceed at fast rates. It is found that the presence of the complex reagent EDTA plays an important role in the morphological changes of nanostructure hydroxyapatite. EDTA acts as a hexadentate unit by wrapping itself around the Ca²⁺ metal ion with, four oxygen and two nitrogen atoms and forms several five member chelate rings. The relative specific surface energies associated with the facets of the crystal determines the shape of the crystal. Scanning electron microscopy revealed the presence of hydroxyapatite nano strips with the range 50‐100 nm in EDTA influenced HAP powders. Fourier transform‐infrared spectroscopy (FT‐IR) result combined with the X‐ray diffraction (XRD) indicates the presence of amorphous hydroxyapatite (HAP) in the as‐prepared material. X‐ray patterns collected on the powder after heat‐treatment at 1100 °C for 2 h in air exhibits single phase of HAP. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical study of Fermi-Pasta-Ulam recurrence for water waves over finite depth

Highly accurate direct numerical simulations have been performed for two-dimensional free-surface potential flows of an ideal incompressible fluid over a constant depth h, in the gravity field g. In each numerical experiment, at t = 0 the free surface profile was in the form y = A ₀cos(2πx/L), and the velocity field v = 0. The computations demonstrate the phenomenon of Fermi-Pasta-Ulam (FPU) recurrence takes place in such systems for moderate initial wave amplitudes A ₀ ≲ 0.12h and spatial periods at least L ≲ 120h. The time of recurrence T _FPU is well fitted by the formula T _FPU(g/h)^1/2 ≈ 0.16(L/h)²(h/A ₀)^1/2.     

Composition of peroxide products in reaction of ozone with cyclohexane

Conclusions A modified iodometric method was developed for determining H₂O₂, hydroperoxides, and peroxides in reaction mixtures. Employing this method, the nature of the peroxide compounds formed in the reaction of ozone and cyclohexane was established, and also the rate of their accumulation. The principal peroxide product in the reaction is cyclohexyl peroxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2104–2106, September, 1976.     

The influence of the crystalline field on the distortion of the octahedral complexes of divalent iron

The analysis of the experimentally observed distortions of the impurity octahedral Fe(II) complexes in the crystalline matrices of various symmetry shows that these distortions are of the Jahn-Teller (JT) nature. The Mössbauer investigation results for the impurity complexes [Fe(H₂O)₆]²⁺ in Cu_I-xFe_xSiF₆ · 6H₂O combined with the similar data for the series of isomorphic compounds MeSiF₆ · 6H₂O (Me=Ni,Zn, Co) indicate that the value of distortion is determined by the crystalline field of the matrix. The sign of the quadrupole splitting on the ferrous nucleus (Δ E_Q < 0) obtained from the (Δ E_Q < O) -resonance measurements on Cu_I-xFe_xSiF₆ · 6H₂O (x < 0,05) in the magnetic field corresponds to the ground orbital singlet, inherent to the systems, when the JT distortion occurs. The ⁵T_2g vibronic instability calculations with the spin-orbit interaction taken into account, confirm the experimental data on the compliance of the Fe(II) octahedral complex; thus it is possible to use this complex as the probe of the intracrystalline fields.     

Synthesis of Polyvinylpyrrolidone under Secondary Inhibition Conditions

A new approach to controlling the molecular weight of polyvinylpyrrolidone in radical polymerization is considered. When the reaction is performed in the presence of a stable nitroxyl radical, 2,2,6,6-tetramethylpiperidyl-1-oxyl, the effect of secondary inhibition is manifested after the end of the induction period. This effect can be used for preparing polymers with prescribed molecular weights.