Development of male germ cells in the fur seal (Callorhinus ursinus)

Three types of spermatogonia have been distinguished in the fur seal: type A, intermediate, type B. The type A spermatogonia are presented by means of five varieties: stem A, A1, A2, A3, A4. The spermatogonia of the stem A type is characterized with presence of equally distributed chromatin in the nucleus. The spermatogonia of the A1-A4 types are characterized with a gradual condensation of chromatin. The intermediate spermatogonia possesses a light nucleus, chromatin as small and large granules is situated near the nuclear membrane. The spermatogonia of B1-B3 types have a round nucleus, their chromatin is granular. Spermatocytes both at the leptotene stage and at the zygotene stage are presented by means of three cellular forms. At the pachytene stage four cellular forms are distinguished. Basing on formation of the acrosomic apparatus, 18 stages of spermatids development are distinguished.     

The effect of sensitization to the electrical activity of the muscles of the lower respiratory tract in the rat

The electrical activity of the smooth muscle of the trachea was studied on sensibilized ovalbumine rats. The role of intramural ganglions of the airway was shown.     

Role of secondary electrons and metastable atoms in the electron-beam activation of argon-silane mixtures

The energy and spatial degradation of the primary beam electrons and the production of high-energy secondary electrons in ionizing collisions are analyzed by solving the Boltzmann integral equation for the electron distribution function. The effect of the primary and secondary electrons on the direct ionization of an Ar-SiH₄ mixture, the production of metastable argon atoms, and the dissociation of monosilane molecules is investigated over a wide range of the beam electron energies, argon pressures, and monosilane concentrations. The influence of metastable Ar* atoms on the dissociation of SiH₄ is studied by using the balance equation for metastable argon atoms and the equation for the ambipolar diffusion of ions and low-energy secondary (plasma) electrons in the beam plasma. It is shown that the main contribution to the activation of an Ar-SiH₄ mixture in an electron-beam plasma is provided by secondary electrons with energies higher than the excitation threshold for argon and the dissociation threshold for monosilane, whereas the contribution from metastable argon atoms, though potentially being comparable with that from secondary electrons, is less than in gas-discharge plasmas.     

A self-consistent kinetic model of the stratification of plane and spherical low-pressure discharges in argon

A self-consistent kinetic model is used to describe the effect of stratification of the positive column of a plane and a spherical gas discharge in argon at low pressure. The model is based on solving the Boltzmann kinetic equation for the electron energy distribution function, the time-dependent ion continuity equation, and Poisson’s equation for the self-consistent electric field. The spatial distributions of the electron and ion densities and of the electric field in the positive column of a stratified discharge are determined. The kinetic mechanism for discharge stratification in noble gases at low pressures is explained in terms of the proposed model. The model makes it possible to describe the moving strata and to confirm the validity of the experimentally obtained dependence of the radii of the strata on their numbers in a spherical discharge.