Specific transport properties of medicinal chitosan films

Processes of water-vapor sorption by medicinal chitosan films and the kinetics of release of antibiotics of the cephalosporin series from these films have been studied. It has been found that the structural changes in the polymer matrix that are related particularly to its chemical modification via the interaction with drugs are the most probable cause of the deviation of the mass-transfer mechanism from the classical Fick’s mechanism.     

Sufficient condition for the hyperbolicity of mappings of the torus

We consider mappings of the m-dimensional torus T^m (m ≥ 2) that are C ¹-perturbations of linear hyperbolic automorphisms. We obtain sufficient conditions for such mappings to be one-to-one hyperbolic mappings (i.e., Anosov diffeomorphisms). These results are used to study the blue-sky catastrophe related to the vanishing of a saddle-node invariant torus with a quasiperiodic winding in a system of ordinary differential equations.     

Stability of liquid flow between heated rotating cylinders

The effect of a radial temperature gradient on stability of steady-state flow of a viscous liquid between two solid concentric cylinders both rotating in the same direction is considered. The linear stability problem is considered in the Boussinesq approximation. Sufficient stability and instability conditions for the flow relative to rotationally symmetric perturbation are obtained. Neutral curves are computed for a wide range of problem parameters.     

Oscillatory rotationally symmetric loss of stability of nonisothermal couette flow

A study is made of the stability of nonisothermal Couette flow — steady flow of a viscous heat conducting fluid between two rotating concentric cylinders heated to different temperatures. The methods of perturbation theory are used to establish conditions sufficient for bifurcation of a neutral curve of oscillatory instability from the neutral curve of monotonic instability. Computer calculations show that for certain values of the parameters of the problem these conditions are realized and there is an oscillatory loss of stability of the nonisothermal Couette flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 76–80, January–February, 1984.I thank V. I. Yudovich for constant interest in the work.     

Stability of nonisothermal couette flow

A study is made of the loss of stability of the stationary flow of a viscous fluid between two heated rotating cylinders. The linearized stability problem is studied in the Boussinesq approximation. The perturbations are assumed to be periodic in the time, and also in the axial and azimuthal directions. The neutral curves are calculated numerically. The ranges of variation of the parameters of the problem are found, and in them the most dangerous perturbations (in the class of spatially periodic perturbations) are those without rotational symmetry.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 167–170, January–February, 1980.I thank V. I. Yudovich for constant interest in the work.     

Charged Particle Trajectories in the MAVR High-Resolution Magnetic Spectrometer

Charged-particle trajectories in the MAVR high-resolution magnetic spectrometer [1] are simulated. The latter has been constructed at the U400 accelerator for purifying the incident beam and identifying the products of nuclear reactions induced by the beams of stable and radioactive nuclei. In this paper we present the MAVRPC software package, aimed at reconstructing the spectrometer focal plane, optimizing the fields of quadrupole and dipole magnets, and estimating the solid-angle acceptance for secondary particles.     

Isotope effects in Raman spectra of crystalline sulfur α-S8

The Raman spectra of ³²S, ³³S, and ³⁴S powders, as well as ^naturS powder with the natural isotopic composition, have been measured in the temperature range of 5–300 K. The isotope mass dependences of the vibrational frequencies have been obtained. It has been shown that such a dependence in the region of mixed translational-librational modes differs from the dependences known for monatomic inorganic crystals. The role of zero-point vibrations for low- and high-frequency modes has been revealed throughout the entire temperature range.