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The aim of the investigation was to assess the level of protein oxidative modification (POM) and lipid peroxidation (LP ) products in muscular tissue of rats with radiation disease when exposed to low-intensity red light. Materials and Methods. We studied the level of direct and induced POM, as well as LP parameters in rat femoral muscular tissue after ionizing radiation exposure and correction of radiation sequellae by low-intensity red light. Free-radical oxidation intensity was estimated by the content of POL products — neutral and basic aliphatic aldehydeand cetone-dinitrophenylhydrazones; the level of LP products — diene conjugates, triene conjugates and Schiff’s bases. SPSS software application package was used for statistical processing. Results. Rat muscular tissue showed the decreased intensity of oxidative processes — POM and LP after the ionizing radiation area had been exposed to low-intensity incoherent red light, i.e., there was the intensification of oxidative processes. The following exposure of the same area to low-intensity red light resulted in decreased level of oxidation products. Conclusion. The exposure of biological tissues to low-intensity incoherent red light after ionizing radiation contributes to the decrease of accumulation of POM and LP products and prevents from ozidative stress development.

Markov and semi-Markov models are widely used in dependability assessment of complex computer-based systems. Model stiffness poses a serious problem both in terms of computational difficulties and in terms of accuracy of the assessment. Selecting an appropriate method and software package for solving stiff Markov models proved to be a non-trivial task. In this paper we provide an empirical comparison of two approaches to dealing with stiffness – stiffness avoidance and stiffness-tolerance. The study includes several well known techniques and software tools used for solving Kolmogorov’s differential equations derived from complex stiff Markov models. In the comparison we used realistic cases studies developed by others in the past: i) a computer system with hardware redundancy and diverse software, and ii) a queuing system with a server break-down and repair. The results indicate that the accuracy of the known methods is significantly affected by the stiffness of the Markov models, which led us to developing a procedure (an algorithm) for selecting the optimal method and tool for solving a given stiff Markov model. The algorithm is, also included in the paper.