Supercritical fluid chromatography and its application to analysis and preparation of high-purity compounds

The principles of supercritical fluid chromatography (SFC) and its application in various fields are reviewed. A comparison of high-performance liquid chromatography (HPLC) and SFC is performed. In discussing the applications, emphasis is placed on the possibility of using SFC in analysis of impurities in pharmaceuticals and biologically important substances and in preparation of high-purity substances. In describing detectors for SFC, special attention is paid to mass-spectrometric detectors.     

Surface tension and equilibrium shape of crystals in a wide range of angles

We have found the angular dependence of the surface tension using simplified models including short-range interaction as well as long-range interaction. The shape of a rounded surface is found in total range of angles as well as sizes of rectilinear (smooth) faces depending on parameters of a model and the temperature. Some dimensionless ratios have occurred to be universal.     

Core level spectroscopy and RHEED analysis of KGd(WO4)2 surface

Structural and electronic characterisation of mechanically polished (010) KGd(WO₄)₂ (KGW) has been produced by reflection high-energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). With XPS analysis the original element binding energies, chemical composition and valence band structure of KGW have been determined.     

Magnetic configurations of hybrid ferromagnetic dot–superconductor systems

In-plane single domain and vortex magnetization configurations of the magnetic dot in the hybrid superconductor–ferromagnet system are considered. Single domain configuration energy shift due to the presence of superconductor is calculated. The change of the phase curve of the ferromagnetic dot magnetization due to the repulsion of the magnetic field by the superconductor is obtained. Up to the two-fold decrease of the ferromagnetic dot critical radius due to the presence of the superconductor is predicted.     

Probing fission time scales with neutrons and GDR gamma rays

The time scales for nuclear fission have been explored using both pre-and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV ¹⁶O + ¹⁷⁶Yb and ²⁰⁸Pb and 104-MeV ⁴He + ¹⁸⁸Os and ²⁰⁹Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF2 array. The pre-and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, γ, and fission time scales. The γ values ranged from 7 to 20, while the fission times were (31–105)×10^?21 s.     

Small-size spectrometer for emission analysis of low-temperature plasma flows

Calculation data for characteristics of concave holographic arrays are reported, allowing development of low-size spectrometers with medium and high spectral resolution. The holographic arrays were fabricated around new subnanostructured films of chalcogenide semiconductors. A medium-resolution, small-size spectrometer was used to measure the distribution of temperature in the gas flow emanating from a DC plasmatorch with sectioned inter-electrode insert by the relative-intensity method. Presently available methods for measuring the temperature of non-uniform optically thin plasma were employed. A comparison of spectral and thermophysical methods for temperature measurements is given.     

Thermodynamic Modeling of Actinide Complexation with Acetate and Lactate at High Ionic Strength

The stability constants of NpO ₂ ⁺ , UO ₂ ²⁺ Am³⁺, and Th⁴⁺ with acetate and lactate anions has been measured in 0.3–5.0m NaCl media at 25°C by the solvent extraction technique. For the 1:1 complexation, the values of the stability constants increased in the order: NpO ₂ ⁺ < Am³⁺ < ₂ ²⁺ < Th⁴⁺, in accordance with the actinide charge density and reflecting the strongly ionic bonding of the complexes. The Pitzer ionic interaction parameters were calculated and used to estimate the thermodynamic stability constants at I = 0. Because our data were collected mainly in the high ionic strength region values of ⁽¹⁾ were estimated from values reported in the literature. For all stability constants the Pitzer model gives an excellent representation of the data using three interaction parameters ⁽⁰⁾, ⁽¹⁾, and COn leave from Institute of     

Two-dimensional commensurate soliton structures

A phase diagram of pinned soliton structures in two dimensions has been found for a repulsive interactionU(x) between solitons withU(x)>0. The critical fugacity of the commensurate soliton structure is shown to be proportional toU(l), wherel is the period of this structure.