Joint consistency in extensions of the minimal logic

Analogs of Robinson’s theorem on joint consistency are found which are equivalent to the weak interpolation property (WIP) in extensions of Johansson’s minimal logic J. Although all propositional superintuitionistic logics possess this property, there are J-logics without WIP. It is proved that the problem of the validity of WIP in J-logics can be reduced to the same problem over the logic Gl obtained from J by adding the tertium non datur. Some algebraic criteria for validity of WIP over J and Gl are found.     

The effect of water vapor on the electrical properties and sensitivity of thin-film gas sensors based on tin dioxide

The results of theoretical and experimental studies into the effect of water vapor on the electrical conductance of a gas sensor and the sensor response to hydrogen action are discussed. A relation describing the dependence of electrical conductance G₀ on absolute humidity in the pure air is derived using a hypothesis of the presence of space-charge regions depleted of electrons between the SnO ₂ grains in a polycrystalline tin dioxide film. Due to dissociative chemisorption of water molecules, the energy-band bending at the SnO ₂ grain interfaces decreases and the oxygen-vacancy concentration in the grains increases, resuling in an increase in G₀. An equation for the sensor response to hydrogen action is derived (the G₁/G₀, ratio, where G₁ is the sensor conductance in a gas mixture containing molecular hydrogen). The expression describes the dependence of G₁/G₀ on the hydrogen concentration in the interval 50–6·10³ ppm, band bending at the SnO ₂ grain interface, and sensor temperature. The dependences of the sensor conductance, highest possible conductance, and energy-band bending on temperature and absolute humidity resulting from processing of the experimental data are in good agreement with the theoretical predictions. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 50–56, August, 2008.     

Square‐wave Voltammetry of Two‐step Surface Electrode Mechanisms Coupled with Chemical Reactions – A Theoretical Overview

Square‐wave voltammetry (SWV) of so‐called “surface redox reactions” is seen as a simple and efficient tool to quantify large number of drugs, physiologically active substances and other important chemicals. It also provides elegant methods to get access to relevant kinetic and thermodynamic parameters related to many lipophilic compounds. Moreover, with this technique we can study activity of various enzymes by exploring the “protein‐film voltammetry” set up. In this work, we focus on theoretical SWV features of four complex surface electrode mechanisms, in which the electron exchange between the working electrode and the studied redox substrate takes place in two successive steps. While we present large number of calculated square‐wave voltammograms, we give hints to recognize particular two‐step surface mechanism, but also to distinguish it from other similar mechanisms. We present plenty of relevant aspects of surface two‐step surface EE, two‐step surface ECE and surface catalytic EEC’ mechanisms. Moreover, we present for the first time a series of theoretical results related to two‐step surface EECrev mechanism (i. e. two‐step surface reaction coupled to follow‐up reversible chemical step). The simulated voltammetric patterns presented in this work can bring relevant aspects to resolve some experimental situations met in voltammetry of many redox enzymes and other important substances whose electrochemical transformation occurs in two‐steps.     

Algorithms for Recognizing Restricted Interpolation over the Modal Logic S4

We consider the restricted interpolation property IPR in modal logics. Earlier, the decidability of IPR over the modal logic S4 was proved and a finite list was found that contains all logics that can possess IPR over S4. However, this list contains some undue logics. The present article gives examples of the logics.

     

Dynamic Vortex States in High-Temperature Superconductors under Pulsed Magnetization

Physics of the Solid State - A vortex system of the Bi-2212 superconductor in an external magnetic field linearly increasing at different rates has been numerically simulated using the Monte Carlo...     

Urea (Polyurea) Greases

The review deals with greases in which organic ureas of various compositions and structures are used as thickeners. The nature of compounds participating in the synthesis of organic ureas and the main types of polyurea thickeners are considered. The physicochemical, tribological, and operation properties of plastic polyurea lubricants are discussed.     

Control of optical properties of biotissues: I. spectral properties of the eye sclera

A method for computer modeling of transmission and diffuse reflection of a strongly scattering biotissue is described. Results of calculations of spectral characteristics for a model of the human eye sclera are presented and compared with experiments. The possibility to control optical properties of biotissues is theoretically substantiated and experimentally confirmed. Variations in color indices of biotissues are calculated using theoretical and experimental spectral characteristics obtained for the eye sclera.     

Controlling optical properties of biological tissues: II. Coherent optical methods for studying the tissue structure

Correlation and polarization properties of dynamic speckle fields formed upon scanning in vitro human sclera samples subjected to immersion agents with a focused laser beam were studied. The immersion agent diffusion into the tissue reduces the relative refractive index of structure-forming elements (collagen fibrils) with respect to the base sclera substance and thus stimulates the passage from multiple to single scattering of a probing beam. Experimental data are presented on the evolution of the autocorrelation function of intensity fluctuations and the intensity ratio between polarized and depolarized components of laser radiation passed through a sclera layer due to artificial clarification of the tissue samples analyzed. Possible applications of the developed method to the tissue structure diagnostics are discussed.