Vibronic interaction in europium nitrates Eu(NO3)3 x 4SOR2

Luminescence and excitation of luminescence vibronic spectra of europium nitrates Eu(NO3)3 x 4SOR2 containing sulphoxide derivatives were obtained and analysed. Some factors influencing the intensity distribution in vibronic sidebands are discussed. Significant variation of the intensity distribution in antiStokes sidebands of Eu3+ electronic transitions in series of nitrates results from the difference in effective charges on coordinated oxygen atoms of ligands. Another important detail of the vibronic spectra is a redistribution of intensity in the region of 5D0, 5D1-->7F2 transitions of luminescence spectra originated in overlap of different vibronic transitions. Mixing between the 7F2 electronic state of Eu3+ and vibronic satellites of 7F0 electronic state was studied both under conditions of resonance and in case of significant detuning.     

Adsorption Properties of Mesoporous Silica Gel with β-Cyclodextrin as a Pore-Forming Agent Relative to Moxifloxacin

A method for the synthesis of mesoporous silica gel using β-cyclodextrin as a pore-forming agent is developed. The physical properties and structure of the obtained adsorbent are studied by Fourier-transform IR spectroscopy and the low-temperature adsorption–desorption of nitrogen (BET) method. The material has an average specific surface area of 435 ± 5 m²/g and an average pore size of 5 ± 0.5 nm. This value of the pore size indicates the formation of complex structures from columnar associates of β-cyclodextrin in the synthesis of the material. The adsorption capacity of the obtained material is 0.2 ± 0.05 mg of 2-hydroxypropyl-β-cyclodextrin per milligram of the adsorbent. The dissociation constant of the complexes of moxifloxacin with β-cyclodextrin inside the pores of silica gel is of the order of 5 × 10^–3 M. The resulting system of SiO₂-β-CD is promising for application in the biomedical chemistry as a carrier of biologically active molecules, particularly as an antibacterial preparation of moxifloxacin.     

Solubility in the system Na2Cr2O7 + 2NH4Cl ⇆ (NH4)2Cr2O7 + 2NaCl-H2O

The solubility in the water-salt quaternary reciprocal system Na₂Cr₂O₇ + 2NH₄Cl ⇆ (NH₄)₂Cr₂O₇ + 2NaCl-H₂O has been investigated for the first time at 25, 50, and 75°C. Using a formal analytical model, the boundaries of the phase fields have been determined, and the univariant lines and invariant points have been calculated. The experimental data have been used to calculate the temperature and concentration parameters of the circular isohydric process of potassium dichromate preparation with the participation of ammonium salts as intermediates.     

Synthesis of pyrrolidines,pyrrolines, and pyrroles

As compounds of potential physiological activity, new sulfamide derivatives, Schiffs bases derived from N-arylpyrrolines, are obtained by reacting sulfanilamide, 2-(p-aminobenzenesulfamide) thiazole, 2-(p-aminobenzenesulfamido)-pyrimidine, and 1-phenyl-3-ethyl-4-methyl-5-(p-aminobenzenesulfamido) pyrazole with -(2-chloroethyl)--chlorocrotonaldehyde.For Part XIV see [1].     

Phase equilibria and extraction of metal cations in the systems based on synergistic mixtures of potassium bis(alkylpolyoxyethylene)phosphate and alkylbenzyldimethylammonium chloride

The solubility in the system formed by the oxyethylated anionic surfactant potassium bis(alkylpolyoxyethylene)phosphate (oxyphos B), the cationic surfactant alkyldimethylbenz- ylammonium chloride (cathamine AB), and water was studied. The optimal parameters of the extraction process in the systems based on the mixture of surfactants, whose aqueous solutions have the lowest phase-separation temperatures, without a salting-out agent and in the presence of (NH₄)₂SO₄ were established. A possibility of the extraction of metal cations in the oxyphos B—cathamine AB—water system at 50 °С, and the (NH₄)₂SO₄—oxyphos B—cathamine AB—water system at 25 °С was demonstrated. The advantages of application of a mixture of ionic surfactants as compared to the systems based on individual surfactants were revealed.     

Cycles of two-dimensional systems: Computer calculations,proofs, and experiments

One of the central problems in studying small cycles in the neighborhood of equilibrium involves computation of Lyapunov’s quantities. While Lyapunov’s first and second quantities were computed in the general form in the 1940s–1950s, Lyapunov’s third quantity was calculated only for certain special cases. In the present work, we present general formulas for calculation of Lyapunov’s third quantity. Together with the classical Lyapunov method for calculation of Lyapunov’s quantities, which is based on passing to the polar coordinates, we suggest a method developed for the Euclidian coordinates and for the time domain. The calculation of Lyapunov’s quantities by two different analytic methods involving modern software tools for symbolic computing enables us to justify the formulas obtained for Lyapunov’s third quantity. For quadratic systems in which Lyapunov’s first and second quantities vanish, while the third one does not, large cycles were calculated. In the calculations, the quadratic system was reduced to the Liénard equation, which was used to evaluate the domain of parameters corresponding to the existence of four cycles (three “small” cycles and a “large” one). This domain extends the region of parameters obtained by S.L. Shi in 1980 for a quadratic system with four limit cycles.     

Double Potential Method for Modeling the Internal Flow of a Viscous Incompressible Liquid

Doklady Mathematics - The problem of numerical modelling water purification from iron impurities is considered. The cleaning task is relevant for many industrial applications, including the...     

Investigation of intermolecular interactions in solutions by means of millimeter-wave spectroscopy 5. Positive and negative hydration effects in aqueous solutions of methylureas

A study has been made of the concentration dependence of absorption of radiation at 5 cm^–1 by aqueous solutions of urea and its N-methyl, N,N-dimethyl, N,N'-dimethyl, and tetramethyl derivatives; and their effective hydration numbers have been calculated. The low values obtained for the effective hydration numbers of urea, N-methylurea, and N,N'-dimethylurea are explained by the close mutual approach of the two hydrogen atoms in the trans position relative to the carbonyl group (negative hydration); in the case of the N,N-dimethyl and tetramethyl derivatives, no negative hydration effect is observed. For the tetramethylurea, very definite hydrophobic hydration is observed. On the basis of data obtained on the effective hydration number, an estimate has been made of the relative contents of different conformers of methylurea and N,N'-dimethylurea in solution.For Previous Communication, See [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 321–326, February, 1990.