Phase equilibria,crystal structure at 1373 K and properties of complex oxides in the Nd–Co–Fe–O system

Phase equilibria in the Nd–Co–Fe–O system were systematically studied at 1373 K in air. The homogeneity range and crystal structure of solid solution NdCo_1–xFe_xO₃ (0.0 ≤ x ≤ 1.0) have been studied by the X-ray powder diffraction method. The structural parameters of complex oxides have been refined by the full-profile Rietveld method. It was shown that all oxides reveal practically stoichiometric oxygen composition within the entire temperature range under investigation. The values of thermal expansion coefficients for the cobaltites NdCo_1–xFe_xO₃ (x = 0.3, 0.7) have been calculated within the wide temperature range in air. Chemical stability of NdCo_1–xFe_xO₃ (x = 0.3, 0.7) in respect to the solid electrolyte materials (Ce_0.8Sm_0.2O_2–δ and La_0.88Sr_0.12Ga_0.82Mg_0.18O3-δ) was examined. Electrical conductivity of NdCo_1–xFe_xO₃ (x = 0.3, 0.7) was measured as a function of temperature within the range 300–1373 K in air. It was shown that substitution of cobalt for iron leads to the decrease of conductivity. The isothermal-isobaric cross-section of the phase diagram for the Nd–Co–Fe–O system at 1373 K in air has been presented.     

Synthesis and Study of Equilenin Derivatives and Modified Analogs

Modified equilenin analogs were synthesized with a view to examine the relation between the structure and biological properties of steroid estrogens. The ¹H and ¹³C NMR signals of six estra-1,3,5,7,9-pentaenes were completely assigned using homo- and heteronuclear correlation NMR spectroscopy. The structure of equilenin methyl ester was determined by X-ray analysis. Among the synthesized steroids, compounds were found which exhibit hypocholesterinemic activity with no uterotropic and hypertriglyceridemic effects.     

Phase equilibria and critical phenomena in the Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>-K<Subscript>2</Subscript>SO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system at 380-400°C: Specifics of ternary phase diagrams with type 2 (p-Q) boundary subsystems

Phase equilibria in Li₂SO₄-KLiSO₄-H₂O and K₂SO₄-KLiSO₄-H₂O ternary systems, which contain type 2 salts (Li₂SO₄, KLiSO₄, and K₂SO₄), were studied at temperature of 380 to 400°C and pressures up to 90 MPa. Homogeneous supercritical (SC) fluids, which propagate from type 2 water-salt subsystems into a three-component region, change to heterogeneous liquid-phase equilibria as a result of the transformation of metastable immiscibility regions into stable equilibria. The heterogenization of SC fluids starts with critical phenomena in saturated solutions. In the K₂SO₄-KLiSO₄-H₂O system, the monovariant critical curve (l₁ = l₂ - s_KLiSO4 )(l_1 = l_2 - s_{KLiSO_4 } ) reveals a temperature maximum at the invariant double critical end point (DCE).     

Solubility and immiscibility behavior in ternary hydrothermal systems with critical phenomena in saturated solutions

Abstract

Liquid-liquid immiscibility occurs widely in water-salt systems as stable and metastable equilibria at sub- and supercritical conditions. The phase behavior of ternary mixtures complicated by metastable immiscibility and by a transition of the metastable immiscibility regions into the stable equilibria is discussed using the experimental data on water-salt systems and theoretically derived complete phase diagrams.     

Numerical investigation of the flow in the cathode melt droplet of electric arc

The role of electromagnetic forces and the forces of viscous friction with the arc plasma flow in the flow formation within the cathode melt is considered within the framework of numerical modelling; a comparative estimation of the separate influence of each of the above forces is carried out. The melt flow pattern is found to form mainly by electromagnetic forces. The character of the effect of electromagnetic forces is determined to a considerable extent by the ratio of the radius of cathode attachment of the arc on the melt droplet and the rod cathode radius.     

Effects of the nature of counterions in solution on interactions of phenoxazones, xanthones, and carbazoles containing benzo-crown groups with DNA

The interactions of DNA with phenoxazones, xanthones, and carbazoles containing the (benzo-18-crown-6)-4′-yl and (benzo-15-crown-5)-4′-yl radicals bonded to the chromophore via spacers of different lengths in the presence of Na⁺ and K⁺ ions were studied by spectrophotometry, circular dichroism, and dynamic birefringence. The thermodynamic parameters of the binding of the compounds with DNA and changes in the macromolecular parameters of the DNA molecule during complexation were determined. Based on the results of these studies, we suggested the models of bonding of these compounds to the double helix of DNA. It is shown that the mode of DNA binding with a phenoxazone derivative containing two (benzo-15-crown-5)-4′-yl radicals bonded via a fragment of glycine to chromophore depends on the type of the counterion in solution. In the presence of Na⁺, the chromophore is intercalated into the double helix of DNA; in the presence of K⁺, it is bound to DNA in the form of a dimer outside the double helix. The type of the counterion does not affect the mode of binding of other crown-containing compounds of actinocin with DNA. For compounds containing the (benzo-18-crown-6)-4′-yl radical, the mode of binding to DNA adepends only on the spacer length.     

A Practical One-Pot Synthesis of Positron Emission Tomography (PET) Tracers via Nickel-Mediated Radiofluorination

Invited for this months cover picture is the group of Professor Bernd Neumaier at the Institute of Radiochemistry and Experimental Molecular Imaging at the University Clinic of Cologne. The cover picture shows the differences in brain metabolism of a healthy young and a healthy old subject, as well as a patient suffering from Parkinsons disease (left to right) uncovered by 6-[¹⁸F]FDOPA-positron emission tomography (PET). Morbus Parkinson occurs when nerve cells that produce dopamine begin to die. The shortage of dopamine leads to movement problems in affected individuals. 6-[¹⁸F]FDOPA is extensively used to evaluate the progression of Parkinsons disease. Bold stick projections of this PET tracer, as well as a neuronal network, are seen in the background. Unfortunately, conventional procedures to produce 6-[¹⁸F]FDOPA are cumbersome. Thus, several recent developments aim at the simplification of this radiosynthesis. In our work, we studied the applicability of the recently reported Ni-mediated radiofluorination approach for daily routine production of 6-[¹⁸F]FDOPA. For more details, see the Full Paper on p. 457 ff.     

Magnetic Moments of Single-Crystal Tb–Sm Alloys

In the present paper, the magnetic properties of Tb_1–xSm_x alloys with different samarium contents are investigated along the <11 [`2]\overline 2 0 > (b), < 10 [`1]\overline 1 0 \gt; (a), and <0001> (c) crystallographic directions in magnetic fields up to 50 kOe in the temperature interval 4.2–400 K. It is demonstrated that small additions of the light rare-earth samarium metal to the heavy rare-earth terbium metal increase the specific magnetization and the effective magnetic moments.