Nitropyrazoles

N-Substituted 3,4-dinitropyrazoles, 1,5-dimethyl-3,4-dinitropyrazole and 1-methoxy-methyl-5-methyl-3,4-dinitropyrazole, undergo nucleophilic substitution when reacted with S-, O-, and N-nucleophiles. The substitution occurs regioselectively at the 3-position, affording products in good yields. Anions of N-unsubstituted 3,4-dinitropyrazoles, 1H-3(5)-methyl-4,5(3)-dinitropyrazole and 1H-4,5(3)-dinitropyrazole, also react in water with S-nucleophiles with regioselective substitution of the nitro groups in the position 3(5).     

Sorption of cesium radionuclides with composite carbon fibrous materials

Sorption of composite sorbents produced by a combined method of thermal treatment and electrochemical and chemical deposition of transition metal ferrocyanides stabilized with latex emulsions onto a fibrous carbon matrix for cesium radionuclides was studied.     

Controllability and observability in the problem of stabilizing steady motions of non-holonomic mechanical systems with cyclic coordinatest

The approach to the solution of stabilization problems for steady motions of holonomic mechanical systems [1, 2] based on linear control theory, combined with the theory of critical cases of stability theory, is used to solve the analogous problems for non-holonomic systems. It is assumed that the control forces may affect both cyclic and positional coordinates, where the number r of independent control inputs may be considerably less than the number n of degrees of freedom of the system, unlike in many other studies (see, e.g., [3–5]), in which as a rule r = n. Several effective new criteria of controllability and observability are formulated, based on reducing the problem to a problem of less dimension. Stability analysis is carried out for the trivial solution of the complete non-linear system, closed by a selected control. This analysis is a necessary step in solving the stabilization problem for steady motion of a non-holonomic system (unlike holonomic systems), since in most cases such a system is not completely controllable.     

The sorption properties of chitosan-carbon fibrous materials

The kinetics and equilibrium of sorption of copper(II) ions on natural biopolymer chitosan, activated carbon fiber, and composite materials prepared by electrochemical modification of activated carbon fibers with chitosan were studied. The influence of the conditions of modification of the microporous carbon matrix on the sorption properties of composite materials with respect to copper(II) was investigated. It was shown that changes in modification conditions could be used to control the sorption properties of chitosan-carbon materials. The mechanisms of copper(II) ion absorption by the sorption materials studied were considered.     

Determining Prefracture Zones at a Crack Tip Between Two Elastic Orthotropic Bodies

The model of prefracture zones is generalized to a crack between two anisotropic materials. An exact analytical solution is found on the assumptions that the prefracture zone is localized on the crack continuation and that only the normal displacements undergo discontinuity in the zone. From this solution, equations for determining the prefracture length and crack tip opening are derived     

Relationship between electrochemical and structural properties of modified carbon fibers

Effect of modification conditions on the electrochemical and structural properties of fibrous carbon materials was studied.     

Thermal isomerization of 2-ethyl-3-bromotetrahydrofuran

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, p. 2896, December, 1991.     

Short-term electrical relaxation in alkaline halide crystals

The temperature dependence of total conductivity in KCl and NaCl monocrystals with calcium impurity in the audio frequency range is studied, It is established that in the temperature range 50–350°C only one of the observed relaxation processes is described by the dipole relaxation mechanism with characteristic time = ₀exp (E/T); the values ₀ = 10^–14sec, E = 0.65eV, and ₀ = 10^–14sec, E = 0.7eV are obtained for KCl and NaCl respectively. Relaxations with values of ₀ and E differing from those above which were observed in the given temperature and frequency range are produced by resistance of the near electrode region.Translated from Izvestiya VUZ. Fizika, No. 6, pp. 101–106, June, 1973.     

Asymmetric hydrogenation on chiral cobalt complexes

Conclusions We were the first to effect the enantioselective hydrogenation of a mixture of isomeric 2-phenylbutenes on chiral cobalt catalytic systems of the Ziegler-Natta type in an optical yield of 25%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2621–2622, November, 1981.