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It has been proven that hydroxyl (OH) radicals can be generated by streamer discharges across water surfaces under ambient atmospheric conditions. Hydroxyl radicals have the highest oxidation capability amongst all oxygen-based reactive species, thus OH play an important role in oxidation of organic molecules and the bactericidal effects of plasma discharges. In this study, generation of hydroxyl radicals in water by pulsed streamer discharges was investigated. Terephthalic acid was used as a chemical probe as this acid is converted into 2-hydroxyterephthalic acid (HTA) by chemical reaction with OH radicals. The concentration of OH radicals was quantified by measuring the fluorescence light intensity generated by HTA molecules in water solutions. Both positive and negative pulsed discharges with different voltage levels were tested. Two different types of sample holder ? non-conductive plastic dishes, and dishes lined with conductive aluminum foil ? were used in order to investigate the effect of the discharge propagation path on the efficiency of OH production. The efficiency of OH production was measured as a function of: the distance between the needle electrode and the water surface; the magnitude and polarity of HV energization; and the total delivered charge. The obtained results will help in optimization of non-thermal plasma systems for chemical and biological decontamination. [ABSTRACT FROM PUBLISHER]

Pulsed electric field (PEF) treatment can be used for non-thermal inactivation of microorganisms. The aim of this paper is to investigate PEF treatment of yeast, Saccharomyces cerevisiae, using three different field waveforms: square; non-oscillating exponential and oscillating exponential. The PEF system used in this paper consists of a pulsed power supply and a parallel-plane metallic electrodes treatment cell located in an air-pressurised chamber. PEF treatment of the yeast was conducted using electric field impulses with magnitudes of 67 kV/cm and 80 kV/cm. The efficacy of the PEF treatment for inactivation of the yeast cells was assessed by comparison of the PEFtreated and untreated yeast populations. Results showed that ~3-log10 reduction in the yeast population can be achieved with 100 impulses using all tested waveforms. Amongst all three tested waveforms non-oscillating exponential impulses demonstrated improved PEF performance. The effect of duration of treatment and peak magnitude of the field on the PEF process is discussed. [ABSTRACT FROM PUBLISHER]