E V Stepanov

Effect of visible light on biological objects: Physiological and pathophysiological aspects

Visible light is a necessary condition for the existence of life on the Earth. The food and oxygen consumed by humans, directly or mediately, are products of photosynthesis: conversion of light energy into the energy of chemical bonding in organic matter. Visible light not only provides photosynthesis in plants; it is also involved in the regulation of many reactions (from molecular to behavioral) in the animal world. This review is devoted to the questions concerning the role of light in the life of biological objects and the physical mechanisms of interaction of visible light with matter. The effect of light on the molecular and physiological reactions of a human and its microflora is analyzed. The existing methods and the application potential of light effects in diagnostics and therapy are considered.

Monitoring of tropospheric ozone in the atmosphere of megalopolises and low-urbanized regions

The results of a long-term study of the ozone content in surface atmosphere, carried out in several regions of the European part of Russia: Karadag Natural Reserve (Crimea); Moscow, Tarusa, St.Petersburg, and Vyatskie Polyany towns; and Karakul’skaya Pristan’ village (Kirov region), are reported. The technical tools used for automatic monitoring of tropospheric ozone and some other atmospheric parameters are described. The main regularities of spatial and temporal variability of tropospheric ozone in atmosphere (in particular, seasonal and diurnal variations; dependences on the concentration of ozone precursors in air, solar light intensity, humidity, and smoke content in atmospheric air; the presence of day and night maxima; the latitude distribution; and the specific features of ozone content dynamics in megalopolises and low-urbanized regions) are demonstrated based on experimental material. The presence of paradoxically high levels of tropospheric ozone near megalopolises is experimentally shown. A general increase in the ozone content in the surface atmosphere is demonstrated. In particular, an increase in the occurrence rate and intensity of cases of hazardous excess above allowable levels of daily average and single maximum allowable concentrations in both megalopolises and resort regions is revealed.

Computer emulation of the method for comparing the isotopic composition of CO2 in gas mixtures based on laser spectral analysis at the 2.05-µm line

An algorithm for processing spectral data in order to determine the isotopic composition of gas mixtures is proposed and simulated using emulated transmission spectra of CO2 in exhaled air tests. It is shown that the ratio of the optical-density spectra of the analyzed and reference gas mixtures is a contrast spectrum with resonant features and a fixed depth of their amplitude modulation. Based on the simulation results several spectral ranges are found to be optimal for analyzing the relative 12CO2 and 13CO2 contents in exhaled air. The effect of random noise on the isotopic analysis result is estimated, and the correlation between the optical density of analyzed gas media, level of random noise, and sensitivity of isotopic analysis is determined. The use of the algorithm proposed reduces the effect of such noises as interference at optical elements, absorption in open atmosphere, drift of the laser pulse envelope, and disbalance of spectral channels. This algorithm is valid for comparative isotopic analysis of any other gas molecules with similar spectral properties.