Platinum(II) Mono-N1-(2"-Tetrahydrofuranyl)-5-Fluorouracilate Complexes with Ammonia

The reaction between cis-[Pt(NH₃)₂Cl₂], N¹-(2"-tetrahydrofuranyl)-5-fluorouracil (HL), and NaOH (taken in a molar ratio of 1 : 1 : 1) or between cis-[Pt(NH₃)₂Cl₂], HL, and Ag₂O (taken in the molar ratio of 1 : 1 : 0.5) was used to synthesize complexes Ia (in the case of NaOH) or Ib (in the case of Ag₂O) with composition Pt(NH₃)₂LCl. The model complex [Pt(NH₃)₃L]NO₃ (II) was synthesized by the reaction between [Pt(NH₃)₃Cl]Cl, HL, AgNO₃, and Ag₂O (1 : 1 : 1 : 0.5). The obtained compounds were characterized by chemical analysis, chromatography, thermogravimetry, conductometry, potentiometry, IR, electronic, and NMR spectroscopies. Complexes Ia and Ib were found to have both similar and different properties. The structures of the compounds and the type of L^– coordination to platinum(II) were suggested. Cytotoxic properties of Iaand Ib were studied.     

Structure of liquid solutions near the critical point

Specific features of the structure of the critical state of binary liquid solutions leading to an anomalous behavior of the Rayleigh line due to a dramatic increase in concentration and density fluctuations are considered. It is shown that an experimental treatment must deal with two fluctuation regions near the critical point of solvent vaporization. In the first region, one can achieve a sufficient degree of accuracy by using theories like selfconsistent field theory. In the second region, which is closer to the critical point than the first region, scaling theory of secondorder phase transitions may be applied. It is found that the anomalous behavior of the Rayleigh line associated with kinetic coefficients is determined by the equilibrium thermodynamic properties and by the radius of fluctuation correlation (rinc). A general theory is developed for calculating thermodynamic potentials, especially the chemical potential and its concentration derivative in the fluctuation region. The results of these calculations are compared with the experimental data briefly described in the paper. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 655–668, July–August, 1998.     

Experimental Verification of the Theoretical Prediction of High‐Temperature Superconductivity in Phases of Titanium Borides TiB k

Theoretical predictions of hightemperature superconductivity (HTSC) in titanium borides, TiBk, have been experimentally verified. These predictions have been reported previously in the form of theoretical phase diagrams. They predicted the existence of HTSC in TiB _k (1.43 < k < 2.57) phases and in TiB_1.5–1.6. An abrupt decrease at 110 K was found on the temperature curve of conductivity R(T) for titanium samples whose surfaces were coated with diffuse layers of depthvariable boride compositions TiB _k . This indicates that the layers include phases possessing HTSC. This behavior of the R(T) curves is explained assuming that the inclusions of HTSC phases have a strong effect on the resistance of the composite materials at T_c. The composition of the boride layers has been investigated by mass spectrometry. Diffuse boride layers were applied to titanium surface by treating its surface with a B₂H₆ + H₂ gas mixture at 610–700°C followed by annealing in vacuum.     

Effect of an alternating field on the relaxation of effect of an alternating field on the relaxation of magnetic flux in a Josephson medium

We establish how trapped magnetic flux depends on the frequency and amplitude of an alternating field and how such a field affects the relaxation rate of the flux. We find that the nature of the flux creep changes in the process and that relaxation of the flux stops after the external field is switched off. We examine the dynamics of flux relaxation in a ring in the approximation in which the current density is assumed homogeneous, for various density dependences of the effective vortex activation energy. The critical current density and the vortex activation energy are obtained as functions of the external field strength. Finally, we explain the observed behavior in terms of the different field profiles emerging in the rings. Zh. éksp. Teor. Fiz. 111, 1047–1056 (March 1997)     

Nonclassical critical indices in the statistical theory of liquids and equations of state with regular and scaling components

Nonclassical critical indices γ = 9/8 and β = 3/8 obtained in works using the statistical theory of liquids are used to approximate data on the isothermal compressibility of ⁴He and SF₆ on critical isochores and binodals, and on the shape of a binodal. The ratio of asymptotic compressibility coefficients Γ ₀ ⁺ /Γ ₀ ^? on critical isochores and binodals is determined from experiments using statistical theory and it is shown that Γ ₀ ⁺ /Γ ₀ ^? coincides with the magnitude of this ratio for linear scaling model with γ = 9/8 and β = 3/8 indices. Highly accurate P-ρ-T data on ⁴He and SF₆ are approximated at these values of the indices using new combined equations of state that include regular and scaling components. The advantage of describing of P-ρ-T data in this manner, compared to describing them with the same equations of state using the critical indices of the three-dimensional Ising model, is demonstrated.     

Structure of liquid solutions near the critical point

Specific features of the structure of the critical state of binary liquid solutions leading to an anomalous behavior of the Rayleigh line due to a dramatic increase in concentration and density fluctuations are considered. It is shown that an experimental treatment must deal with two fluctuation regions near the critical point of solvent vaporization. In the first region, one can achieve a sufficient degree of accuracy by using theories like self-consistent field theory. In the second region, which is closer to the critical point than the first region, scaling theory of second-order phase transitions may be applied. It is found that the anomalous behavior of the Rayleigh line associated with kinetic coefficients is determined by the equilibrium thermodynamic properties and by the radius of fluctuation correlation (r_c). A general theory is developed for calculating thermodynamic potentials, especially the chemical potential and its concentration derivative in the fluctuation region. The results of these calculations are compared with the experimental data briefly described in the paper. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 4, pp. 655–668, July–August, 1998.     

Statistics of avalanches in the self-organized criticality state of a Josephson junction

Magnetic flux avalanches in Josephson junctions that include superconductor-insulator-superconductor (SIS) tunnel junctions and are magnetized at temperatures lower than approximately 5 K have been studied in detail. Avalanches are of stochastic character and appear when the magnetic field penetration depth λ into a junction becomes equal to the length a of the Josephson junction with a decrease in the temperature. The statistical properties of such avalanches are presented. The size distribution of the avalanches is a power law with a negative noninteger exponent about unity, indicating the self-organized criticality state. The self-organized criticality state is not observed in Josephson junctions with a superconductor-normal metal-superconductor (SNS) junction.