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Geochemical, cosmochemical, geophysical, and mineral physics data suggest that iron (or iron–nickel alloy) is the main component of the Earth’s core. The inconsistency between the density of pure iron at pressure and temperature conditions of the Earth’s core and seismological observations can be explained by the presence of light elements. However, the low shear wave velocity and high Poisson’s ratio of the Earth’s core remain enigmatic. Here we experimentally investigate the effect of carbon on the elastic properties of iron at high pressures and temperatures and report a high-pressure orthorhombic phase of iron carbide, Fe7C3. We determined the crystal structure of the material at ambient conditions and investigated its stability and behaviour at pressures up to 205 GPa and temperatures above 3,700 K using single-crystal and powder X-ray diffraction, Mössbauer spectroscopy, and nuclear inelastic scattering. Estimated shear wave and compressional wave velocities show that Fe7C3exhibits a lower shear wave velocity than pure iron and a Poisson’s ratio similar to that of the Earth’s inner core. We suggest that carbon alloying significantly modifies the properties of iron at extreme conditions to approach the elastic behaviour of rubber. Thus, the presence of carbon may explain the anomalous elastic properties of the Earth’s core.

Abstract: The morphological properties of floodplains and their morphological classification are shown from the generalization of long-term studies. A detailed description of alluvial processes is given, and stages of alluvial soil formation are characterized. Zonal-geographic, hydro-geomorphologic, evolutionary, and geomorphologic-genetic regularities in soil geography are found. The properties of alluvial soils under sharply contrasting climatic conditions, e.g., humid and arid, are considered. The high biogenic ability of soils and intensity of the soil-forming process in floodplains are proved. Data characterizing the structure and properties of floodplain soils in particular river valleys and the main micromorphological diagnostic features of alluvial soils are given.

Abstract: The interaction of polyampholyte propylenimine dendrimers of five generations containing peripheral carboxyl and inner tertiary amino groups with lightly crosslinked highly swelling polyelectrolyte gels has been studied. It has been shown that the polyampholyte dendrimers of all five generations are efficiently sorbed by a polyanion sulfur-containing hydrogel (below the isoelectric point) and a polyamine hydrogel (above the isoelectric point) to give rise to interpolyelectrolyte complexes. The composition of interpolyelectrolyte complexes and the equilibrium concentration of the dendrimer in the surrounding solution are appreciably affected by the pH of the medium. Amount of zwitterion pairs in a dendrimer molecule significantly influence the formation of interpolymer salt bonds. The polyampholyte dendrimer can pass from an anionic hydrogel to a cationic one upon a small change in pH near the isoelectric point.

Thermolysis of hexachlorocyclohexane in a flow-through packed system in an inert gas atmosphere was studied.

This article discusses findings obtained regarding the effect of a hydrodynamic field on the reduced viscosity, effect of turbulent friction reduction, light scattering, double refraction, and optical density of aqueous solutions of hydrolyzed polyacrylamide.

It is found that degradation in aqueous polyethylene oxide is accompanied by dehydration and aggregation, with deterioration in the thermodynamic affinity for water, which is not related to molecular-mass reduction.

Conclusions 1.A study had been made of hydrogen exchange in 1,1'-di-tert-butylcobalticinium borofluoride, and 1,1',3,3' -tetra-tert-butylcobalticinium borofluoride, in MeOD+DMSO+MeOK. The hydrogen atoms of the cyclopentadienyl (Cp) ring of the tert-butyl-substituted cobalticinium salts retain their ability to exchange for deuterium, the situation here differing from that met in the methyl-substituted cobalticinium salts.2.The rates of isotopic hydrogen exchange have been used to estimate the acidity of the Cp-ring C-H bonds in 1,1'-di-tert-butylcobalticinium tetrafluoroborate and in 1,1',3,3'-tetra-tert-bu1ylcobalticinium tetrafluoroborate.

1.The IR spectra of crystalline nickelecene and cobalticene, as well as the Raman spectrum of nickelecene, were obtained at low temperatures, and an interpretation of them was given.2.The fine structure of the IR bands of nickelecene at low temperatures agrees with the x-ray diffraction data, obtained for the crystal at R~20‡.3.In the Raman spectrum of nickelecene in comparison with other metallocenes, a reverse order of arrangement of the frequencies of the metal-ring vibrations?4 and?16 is observed.

1.The reaction of isotopic exchange of hydrogen of two types of bis-p-arene complexes of chromium (Arene)2Cr (where Arene=benzene, toluene, ethylbenzene) with deuteroethanol in the presence of sodium ethylate and [(Arene)2Cr]?I? with deuterium oxide in the presence of KOD, was studied. The rate of isotopic exchange of the hydrogen of both types of chromium complexes increases in proportion to the concentration of the bases, and not only the hydrogen atoms of the aromatic ring, but also the hydrogens of the side chain participate in the exchange.2.The factors of the partial rate were determined for the phenyl and methyl hydrogen atoms in bisp-toluenechromium. On the basis of the data of IEH, the acidity of the C-H bonds in bis-p-benzenechromium was estimated (pKa26.3 +- 0.2).

1.Study of isotopic hydrogen exchange in p-cyclopentadienyl-p-dicarbollylcobalt in basic solution has shown that the hydrogen of the C-H bond of the dicarbollyl ligand enters into reaction 100 times more rapidly than the hydrogen of the cyclopentadienyl ligand.2.These are protophilic substitution reactions, the IHE rate of the dicarbollyl and cyclopentadienyl ligands correlating linearly with the solution basicity.3.CH-bond acidities of the dicarbollyl and cyclopentadienyl ligands of p-cyclopentadienyl-p-dicarbollylcobalt have been determined.4.Substitution of a dicarbollyl ligand for one cyclopentadienyl ligand in the cobalt bis-p-dicarbollylcobalt complex markedly reduces the CH-acidity of the other cyclopentadienyl ligand.

1.A study has been made of the hydrogen exchange reaction of tertiary, secondary, and primary alkyl trifluoracetates (tertiary butyl, methylcyclohexyl-, 2-methylpentyl-, secondary butyl-, isopropyl-, and n-butyltrifluoracetates) in trifluoracetic acid.2.The tertiary alkyl trifluoracetates enter into a hydrogen exchange reaction with trifluoracetic acid. Hydrogen exchange of secondary trifluoracetates can be produced only by increasing the acidity of the medium by adding sulfuric acid to the trifluoracetic acid solutions. The primary trifluoracetates are incapable of hydrogen exchange even under these conditions.3.The proposal is made that hydrogen exchange of tertiary and secondary trifluoracetates is the result of ionization of these esters to form carbonium ions that are capable of exchange.

Summary 1.A study has been made of the hydrogen exchange between tert-alkyl bromides and acetic acid (tert-butyl bromide, 2-methyl-2-bromobutane, 2-methyl-2-bromopentane). The same regularities have been observed in the hydrogen exchange as in the sn1 solvolysis, which confirms that the hydrogen exchange takes place via the carbonium ion.2.The rate of hydrogen exchange of tert-butyl bromide and 2-methyl-2-bromopentane with acetic acid in the presence of HgBr2 and SnBr4 has been studied at 20, 30, and 40°. The rate of the reaction catalyzed by HgBr2 is twice as high as that catalyzed by SnBr2.3.A study has been made of the hydrogen exchange between tert-butyl bromide and acetic acid in the presence of GeBr4 and between 2-methyl-2-chloropentane and acetic acid in the presence of GeCl4. It has been shown that GeBr4 and GeCl4 do not accelerate the hydrogen exchange under these conditions, i.e., they do not exhibit their coordination-valency unsaturation.

1.An investigation was made of the hydrogen exchange of alkyl halides in media differing in dielectric constant, namely formic and acetic acids.2.Tertiary halides (chloride, bromides, and iodides) undergo hydrogen exchange with formic acid-d, whereas secondary alkyl halides do not undergo hydrogen exchange under the same conditions. Tertiary chlorides do not undergo hydrogen exchange with acetic acid-d, whereas under the same conditions tertiary bromides exchange hydrogen atoms for deuterium, though at a much lower rate than with formic acid.3.It is suggested that the hydrogen exchange of alkyl halides is a consequence of their dissociation, which depends on the dielectric constant of the medium, the nature of the halogen atom, and the structure of the alkyl group.

1.We have studied the kinetics of hydrogen exchange in 2-chloro-2-methylpentane and 1-chloro-1 -methylcyclohexane in anhydrous acetic acid in the presence of the Lewis acids: FeCl3, SbCl5, SnCl4, ZnCl2, HgCl2, and BF3. Under the same conditions, the rate constants of hydrogen exchange in the alkyl chlorides depend essentially on their structures.2.On the basis of the results of hydrogen exchange in different tert-alkyl chlorides we have arranged a series of relative activities FeCl3 =SbCl5 > SnCl4 > ZnCl2> HgCl2 > BF3.3.The relative activities of the different Lewis acids remain constant for the tert-aliphatic chlorides and differ only somewhat for the alicyclic chloride.4.We have suggested that the method of hydrogen exchange is suitable for quantitative estimation of the Lewis acids.

Summary 1.The possibility of applying the hydrogen-exchange reaction in the study of the, mechanism of heterolytic reactions was investigated. A study was made of hydrogen exchange a) in the hydrolysis of tertiary alkyl iodides (tert-C4H9I and tert-C5H11I) with water enriched with deuterium oxide, and b) during the exchange of iodine for another iodine atom in alkyl iodides (C2H5I, i-C3H7I, tert-C4H9I, and tert-C5H11I) in reaction with 56% HI enriched with deuterium iodide.2.It was shown that hydrogen exchange in C-H bonds is observed in those reactions which, according to kinetic investigations, proceed by a unimolecular mechanism, i.e. with intermediate formation of carbonium ions. It was shown, in particular, that the hydrolysis of tertiary alkyl iodides (C4H9I and C5H11I) and replacement of iodine by iodine in tertiary alkyl iodides, which proceed by an SN1 mechanism, are accompanied by hydrogen exchange reactions of secondary and primary alkyl iodides, which permits us to assume a bimolecular mechanism for these reactions.

Abstract: Threatened abortion at the early critical terms of gestation is characterized by drastic changes in the antioxidant status of the blood: activation of the pentose phosphate pathway of energy metabolism in erythrocytes and intensification of lipid peroxidation in erythrocytes and plasma.

Conclusions A highly dense ceramic based on the eutectic composition of the Al2O3-ZrO2 system was obtained using 3 mole % Y2O3 addition. The ceramic has a fine-grained structure and high hardness and strength.

1.The rate constants for the deuterium and tritium exchange of nickelocene (NC), ferrocene (FC), triphenylmethane (TPM) and diphenylmethane (DPM) with bases were measured, and it was established that the kinetic acidity of these compounds and cyclopentadienylmanganese tricarbonyl (CMT) increases in the order: FC « CMT < DPM < TPM < NC.2.The kinetic isotope effect for the exchange reaction of NC with bases was determined, the same as in the case of FC and CMT; the reaction proceeds by the mechanism of protophilic hydrogen substitution.

The acidity of niccolocene in dimethyl sulfoxide-methanol solution during potassium methoxide catalysis was determined by measuring the isotopic hydrogen-exchange rate constants of 9-phenylxanthene and niccolocene in this mixture of solvents.

The positive charge on the cobalt atom in the di-p-cyclopentadienyl complex of cobalt exerts a noticeable effect on the rate of hydrogen isotope exchange of the cyclopentadienyl ligand in basic media: the acidity of the C-bonds of cobalticene was estimated.

1.The kinetics of the hydrogen exchange of methylcyclohexane was studied in solutions of trifluoroacetic and sulfuric acids at various values of the acidity function of the initial solutions.2.A linear relationship was found between the acidity functions of the solutions and the logarithms of the rate constants of the hydrogen exchange of methylcyclohexane.

An algorithm has been given for optimizing the performance of a data-measuring system, which provides a simple formulation for computer use.