Methods for the determination of local anesthetic agents

The main methods for the determination of local anesthetics are considered, and their advantages and disadvantages are discussed. After the systematization of published data, it was established that the greatest number of works were devoted to the determination of novocaine, lidocaine, and ultracaine; therefore, methods for their determination are considered separately. It was demonstrated that the extraction and sorption preconcentration of local anesthetics as ion associates with chromogenic organic reagents is promising. It was substantiated that the development of combined rapid and sensitive extraction-photometric, sorptionspectroscopic, and colorimetric methods for the determination of novocaine, lidocaine, and ultracaine with chromogenic organic reagents in different test materials is a problem of considerable current interest.     

Unusual examples of methane hydrate nucleation in bilayer water–oil systems

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Mathematical Modeling of Corrosive Alloy Cracking on the Basis of Generalized Dimensionless Electrochemical Factor

A new generalized dimensionless electrochemical factor of corrosive alloy cracking was developed and a quantitative theory of corrosive-mechanical destruction was constructed on its base. The existence of a threshold value of the proposed factor, above which there is no corrosion cracking, was revealed.     

Thermodynamics of liquid-crystalline solutions of hydroxypropyl cellulose in water and ethanol

Phase diagrams were constructed and comprehensive thermodynamic analysis was performed for hydroxypropyl cellulose-water and hydroxypropyl cellulose-ethanol systems with the use of the static sorption, calorimetry, cloud-point, polarization microscopy, and X-ray diffraction analysis techniques and the measurement of transmitted polarized light intensity. The concentration dependences of the enthalpy, entropy, and Gibbs energy of the formation of liquid-crystalline phases in the systems were determined. It was found that the formation of liquid-crystalline solutions of hydroxypropyl cellulose in water is associated with the energy term of interaction between the components and that in ethanol solutions is due to changes in combinatorial entropy.     

Polymerization of 1-vinyl-3-amino-1,2,4-triazole and some properties of related polymers

The kinetics of radical polymerization of 1-vinyl-3-amino-1,2,4-triazole was studied. The results show that the presence of the amino group as a substituent on the heterocycle decreases the polymerization activity of the triazole-containing monomer. It was found that water has an accelerating effect on the 1-vinyl-3-amino-1,2,4-triazole polymerization process. The substitution of the amino group on the triazole cycle enhances the hydrophilic properties of the polymer relative to those of unsubstituted polyvinyltriazole and opens up possibilities for its further modification.     

Optimization of the structure of a vibration shield under the influence of a concentrated harmonic load

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 142–148, September–October, 1991.     

An atomistic level description of guest molecule effect on the formation of hydrate crystal nuclei by <Emphasis Type="Italic">ab initio</Emphasis> calculations

In the present study, we report the results of a systematic investigation of cage-like water structures using the first-principles calculations. These results show that, in the case of methane hydrate, the following nucleation mechanism can be revealed. The formation of small water cavities filled with methane is the first step of the formation of methane hydrate. It is not necessary to occupy all dodecahedral cages by guest molecules. After that small cavities start to form the H-bonding network with surrounding water molecules and a small number of water molecules is enough for the formation of a stable hydrogen-bonding network. The structural information contained in such nuclei is conserved in the forming crystal. Moreover, the presence of a methane molecule between small cages is also important to prevent the adhesion of cavities. It found that the ozone molecule can also stabilize the small cage since the value of the interaction energy between the ozone guest and the water host framework is very close to that obtained for the methane case. However, ozone affects the structure of large cavities and hence, the second guest is necessary to stabilize the hydrate structure.     

Chemical properties of N-2-Sulfoethylchitosan with a medium degree of substitution

A method was developed for the preparation of N-2-sulfoethylchitosan (SECH) via synthesis in a gel with the use of the reaction of chitosan and sodium 2-bromoethanesulfonate. This method makes it possible to conduct a polymer-like transformation without any acid or base. The structures of the obtained polymers were confirmed via IR and ¹H NMR spectroscopy. The study of the sorption of Ag⁺, Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, Cd²⁺, Pb²⁺, Mn²⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ ions that were crosslinked by SECH during their joint presence in an ammonia-acetate buffer solution showed high values of selectivity in relation to those of silver(I) and copper(II). The selectivity of the sorption of silver(I) ions with respect to copper(II) ions increased with an increase in the degree of substitution of SECH.     

Functionalized derivatives of dibenzo [c,j] dipyrazolo-[3,4-f∶3′,4′-m] [1,2,5,8,9,12] hexaazacyclotetradecinate

A number of derivatives of dibenzo [c,j] dipyrazolo [3,4-f3,4-m] [1,2,5,8,9,12]-hexaazacyclotetradecinate with peripheral nitro, amino, and acetylamino groups have been synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 106–114, January, 1984.     

13-Amino-1,4,7,10-benzotetraoxa-15-cyclododecene

A separation was performed for benzo-12-crown-4 and dibenzo-24-crown-8 obtained as a mixture by the reaction of pyrocatechol with 1,8-dichloro-3,6-dioxaoctane. Nitro and amino derivatives of benzo-12-crown-4 were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 182–183, February, 1985.