Mathematical model of the direct current amplification mode in a channel of a microchannel plate

The boundary-value problem is solved for electric field in a channel of a microchannel plate for a preset value of current at the channel entrance. Analytic equations are determined for the distributions of field, potential, and current along the channel, as well as for the current gain and the current in the circuit of the source of constant voltage as a function of the input current.     

Linear stationary control systems over the Boolean semiring and their graphs of modules

We consider linear stationary dynamical systems over the Boolean semiring. We analyze the properties of complete observability, identifiability, attainability, and controllability of a system. We define the notion of the “graph of modules” of totally controllable totally attainable Boolean linear stationary systems by analogy with spaces of modules in the case of systems over fields. The above-mentioned graph is described in the simplest case of one-dimensional inputs and outputs. We prove the weak connectedness of this oriented graph.     

Preparation of mesoporous silicon dioxide with high specific surface area

The influence of the reactant ratio on the specific surface area, total pore volume, and mean pore diameter of mesoporous silicon dioxide prepared by the sol-gel method was examined. The optimal reactant ratio for preparing the material with a high specific surface area was determimed.     

Unusually Facile Pyrrolization of 2-Acetylcoumarone Oxime with Acetylene

The oxime of 2-acetylcoumarone reacts with acetylene under pressure in the system KOH-DMSO unusually readily forming 2-(2-pyrrolyl)coumarone and the corresponding O-vinyl oxime. Under more rigid conditions 2-(1-vinyl-2-pyrrolyl)coumarone is formed. The possibility of a two-stage transformation of 2-acylcoumarones into 2-pyrrolylcoumarones has therefore been demonstrated for the first time.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 524–529, April, 2005.     

On finite groups isospectral to simple symplectic and orthogonal groups

The spectrum of a finite group is the set of its element orders. Two groups are said to be isospectral if their spectra coincide. We deal with the class of finite groups isospectral to simple and orthogonal groups over a field of an arbitrary positive characteristic p. It is known that a group of this class has a unique nonabelian composition factor. We prove that this factor cannot be isomorphic to an alternating or sporadic group. We also consider the case where this factor is isomorphic to a group of Lie type over a field of the same characteristic p.     

Tunnel spectroscopic measurements in air with a scanning tunnel microscope

Central methodical and hardware problems in taking spectra of different types with a scanning tunneling microscope in air are briefly discussed. Ways to overcome these problems are considered. A procedure for recording a new type of tunneling spectra, namely, voltage-height (U-H) curves, which allow the estimation of the probe-specimen gap, is offered. It is suggested that the current flowing in the course of measurements in air is of electrochemical nature. Different tunnel spectra for metal, oxide, carbon, and polymer materials, including heterogeneous substances, are presented to illustrate the experiments.     

Kinetic, optical, and elastic properties of La0.60Eu0.07Sr0.33MnO3

An experimental study is reported of the temperature dependences of the electrical resistivity and magnetoresistance, thermal and magnetothermal EMF, the Hall effect, optical reflectance, sound velocity, and internal friction of polycrystalline lanthanum manganite La_0.60Eu_0.07Sr_0.33MnO₃ carried out within the 77–430-K temperature range. Substitution of a small amount of europium for lanthanum has been found to result in a considerable decrease in the resistivity and a change in the behavior of its temperature dependence. Four characteristic temperatures at which special features are observed in the above properties have been identified. The discussion of the conduction mechanisms involved is based on the concept of mobility edge motion.