a b s t r a c tCold atmospheric plasma treatment of microorganisms and living tissues has become a popular topic in modern plasma physics and in medical science. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for treatment of skin diseases, open injuries and dental caries. Because of their enhanced plasma chemistry, Dielectric Barrier Discharges (DBDs) have been widely investigated for some emerging applications such as biological and chemical decontamination of media at ambient conditions. Despite the high breakdown voltage in air at atmospheric pressure, the average current of DBD discharges is low. Therefore, a DBD can be applied in direct contact with biological objects without causing any damage. In this work a 60 Hz DBD reactor, which generates cold atmospheric plasma inside Petri dishes with bacterial culture, is investigated. Samples of Staphylococcus aureus, a Gram-positive bacterium and Escherichia coli a Gram-negative bacterium were selected for this study. The bacterial suspensions were evenly spread on agar media planted in Petri dishes. The reactor electrodes were placed outside the Petri dish, thus eliminating the risk of samples microbial contamination. The covered Petri dish with agar medium in it serves as dielectric barrier during the treatment. The plasma processing was conducted at same discharge power (∼ 1.0 W) with different exposure time. Sterilization of E. coli and S. aureus was achieved for less than 20 min. Plasma induced structural damages of bacteria were investigated by Scanning Electron Microscopy.

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This paper proves that uniform spaces and admissible spaces form the same class of topological spaces. This result characterizes a completely regular space as a topological space that admits an admissible family of open coverings. In addition, the admissible family of coverings provides an interesting methodology of studying aspects of uniformity and dynamics in completely regular spaces.

Abstract. Let M and N be admissible Hausdorff topological spaces endowed with admissible families of open coverings. Assume that S is a semigroup acting on both M and N. In this paper we study the behavior of limit sets, prolongations, prolongational limit sets, attracting sets, attractors and Lyapunov stable sets (all concepts defined for the action of the semigroup S) under equivariant maps and semiconjugations from M to N.

The present paper is dedicated to the study of various aspects of attraction and stability for semigroup actions on topological spaces. The main purpose is to present the connections among the distinct notions of attractors and stable sets. The concept of Conley attractor is also investigated and related to the other notions of attractors. All the results are applied to the theory of control systems.