Studying Specific Features of the Resonance Structure of the Background Noise Spectrum in the Frequency Range 1–10 Hz with Allowance for the Slope of the Earth’s Magnetic Field

We present new data on midlatitude features of the resonance structure of the magnetic ultralow-frequency noise spectrum in the frequency range 0.1–10 Hz, namely, the different frequency scale and frequency shift of the resonance-structure maxima for the East-West and North-South components. Resonance spectra of the magnetic components and polarization parameter of magnetic noise for the plane-stratified ionosphere model are numerically simulated with allowance for the inclination of the Earth's magnetic field on the basis of the International Reference Ionosphere IRI-2001 standard. Dependence of the calculated parameters of the resonance structure in the magnetic-component spectra on the source direction and inclination angle of the Earth's magnetic field is explored. The calculations make it possible to explain the different behavior of resonant oscillations in the linear-component spectra and the features of the resonance structure in the background-noise polarization parameter. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 7, pp. 575–584, July 2008.     

Sulfur-containing polymer and carbon materials based on poly(vinyl chloride)

New sulfur-containing copolymers based on poly(vinyl chloride) have been prepared by the nucleophilic substitution of chlorine atoms by sulfur atoms using sodium tetra- and pentasulfides. It has been shown that these copolymers can be carbonized to produce sulfur-containing carbon materials with residual chlorine content about 2 wt %.     

Tris(5-bromo-2-methoxyphenyl)bismuth dicarboxylates [(C<Subscript>6</Subscript>H<Subscript>3</Subscript>(Br-5)(MeO-2)]<Subscript>3</Subscript>Bi[OC(O)CHal<Subscript>3</Subscript>]<Subscript>2</Subscript> (Hal = F,Cl): synthesis and structure

Tris(5-bromo-2-methoxyphenyl)bismuth dicarboxylates [(C₆H₃(Br-5)(MeO-2)]₃Bi[OC(O)CHal₃]₂, Hal = F (II) and Cl (III), have been synthesized by the reaction between tris(5-bromo-2-methoxyphenyl)bismuth (I) and trifluoroacetic acid and thrichloroacetic acid, respectively, in the presence of hydrogen peroxide in ether. According to X-ray diffraction data, a crystal of complex I contains two types of crystallographically independent molecules (a and b) both with a trigonal pyramid configuration. The bismuth atoms in complexes II and III have a distorted trigonal bipyramidal coordination with carboxylate substituents in axial positions. Axial OBiO angles are 166.3(3)° (II) and 171.6(2)° (III); equatorial CBiC angles are 118.0(3)°–123.1(3)° (II) and 113.6(3)°–127.4(3)° (III). Bi–C bond lengths are 2.189(7)–2.200(8) Å (II) and 2.190(8)–2.219(7) Å (III), and Bi–О distances are 2.280(6), 2.459(16) Å (II) and 2.264(5), 2.266(5) Å (III). Intramolecular contacts between the central atom and the oxygen atoms of carbonyl groups (Bi···O 3.028(9), 3.162(9) Å (II); 3.117(9), 3.202(9) Å (III)) are observed at maximum equatorial angles. The oxygen atoms of methoxy groups are coordinated to the bismuth atom. The Bi···O distances in complexes II and III (3.028(16), 3.157(16), 3.162(16) and 3.17(16), 3.143(16), 3.202(16) Å, respectively) are slightly longer than in complex I (3.007(9)–3.136(4) Å).     

Electrosurface properties of tungsten(VI) oxide in electrolyte solutions

Electrosurface characteristics of tungsten oxide in solutions of 1: 1 electrolytes are studied in a wide range of concentration and pH values. The dependence of the position of isoelectric point on the concentration of background electrolyte and the cation nature is revealed. The equilibrium constants of surface reactions, adsorption potentials of ions, specific surface conductivities, and degrees of dissociation of surface groups in the point of zero charge are calculated.     

Analysis of the single-particle energies of 1<Emphasis Type="Italic">f</Emphasis> and 2<Emphasis Type="Italic">p</Emphasis> proton states in <Superscript>64,66,68</Superscript>Zn nuclei by the mean field model with dispersive optical potential

Single-particle proton energies near the Fermi energy in ^64,66,68Zn are analyzed using the mean field model with dispersive optical potential. Good agreement is obtained between the calculated energies and experimental data. The set of parameters of the dispersive optical potential is compared with the set found for neighboring ^58,60,62,64Ni with the magic number Z = 28.     

Seasonal variations of the composition,structural features,and antitumor properties of polysaccharides from <Emphasis Type="Italic">Padina pavonica</Emphasis> (Lebanon) as a function of composition

The variation of the polysaccharide composition of the brown alga Padina pavonica from the Mediterranean Sea was studied as a function of the collection season (April–July). It was shown that the principal polysaccharide (8.0-13.3% of dry alga weight) was alginic acid. Its content did not undergo significant changes from April to July. The content of water-soluble polysaccharides (laminarans and fucoidans) was low (<0.3% of dry alga weight). Water-soluble polysaccharides of the studied alga were practically pure fucoidan. The amount of laminarans was insignificant (<0.01% of dry alga weight). The content of fucoidans increased in alga samples from May through July. It was shown that P. pavonica is a promising source of alginic acids, which have a high capacity for gelation, and fucoidans, which exhibit antitumor action against RPMI-7951 human melanoma cells.     

Dynamic Intramolecular Rearrangements with Proton Transfer in Methanimine Oxide

The structures of possible intermediates and transition states on the potential energy surface for the isomerization of methanimine oxide into formamide were determined by UHF/6-311G(3d) quantum-chemical calculations. Two possible reaction channels were revealed. The same processes were studied by the direct molecular mechanics method which also revealed two reaction channels. The time range of the examined dynamic processes was estimated at 90–300 fs.     

Investigation of special features of the neutron and proton shell structure of the isotopes 90,92,94,96Zr

The neutron and proton single-particle energies and the occupation probabilities for the valence states of the even-even isotopes ^90,92,94,96Zr are determined by matching data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. The data obtained in this way suggest the magicity of the number N = 56 for Z = 40. The single-particle energies of all bound neutron and proton states in the ^90,92,94,96Zr nuclei are described within the experimental errors on the basis of the dispersive optical model.