Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

The Discovery of Thin-Layer Chromatography by N.A. Izmailov and M.S. Shraiber

JPC – Journal of Planar Chromatography – Modern TLC - The discovery of thin-layer chromatography by N.A. Izmailov and M.S. Shraiber, and their contribution to the development of this...     

Electrochemical synthesis of sodium hexamethoxyniobate

Anodic dissolution of niobium in anhydrous methanol in the presence of sodium methylate was studied. A method for recovery of niobium methylate from sodium hexamethoxyniobate by the reaction with ammonium chloride was developed.     

Frontal elution and frontal displacement methods in thin-layer chromatography and their use in concentrating of impurities

A new method of TLC is proposed for concentrating and separating diluted solutions of samples. Samples being analyzed are concentrated in a narrow band on a plate using the displacement version of TLC the aim of lowering the detection limit of the impurities. We compare the frontal elution described in the first work on TLC by Izmailov and Shraiber with the frontal displacement suggested in this work for concentrating diluted solutions of samples and their further separation by linear TLC. It is demonstrated that using displacement TLC in the analytical process allows us to raise the efficiency of separating the compounds under study, and to lower their detection limit by a factor of 10³. We conclude that the use of this approach for the determination of impurities in TLC is advisable in analytical practice.     

Molecular Recognition in Solutions of Rod‐Like Copolymers with Two Different Sequences

Segregation in a solution of rigid copolymeric molecules with two different sequences leading to co‐existence of two smectic mesophases has been studied. Thermodynamic characteristics of these mesophases and their equilibrium compositions were found in the frame of two discrete models. It was shown that the degree of ordering in the mesophase depends on the sequence of units in the identical molecules forming this mesophase. The concentration of “mismatched” molecules in the mesophase (the purity of mesophase) is determined both by the composition and the sequence of such molecules. It was shown, that a difference in the sequences can be sufficient to cause phase separation.

     

Main Directions of Development and Practical Usage of Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatography is one of the most efficient analysis methods that have remained very popular for many decades, despite...     

Application of Track Membranes to Fabricate Potassium Dihydrogen Phosphate Microstructures

A method to fabricate insulator microstructures from aqueous solutions using track membranes as a template has been developed by an example of potassium dihydrogen phosphate. It is shown that microstructures are formed in pores of a track membrane under conditions of forced flow of supersaturated crystallization solution through this membrane. These microstructures continue to grow beyond the pore volume, mainly on the membrane side facing the flow. Their transverse sizes and growth direction are determined by the direction and diameter of membrane pores.