Broad biological activities of "plasma-activated water" (PAW) have drawn great attentions recently. Treatment of water using gas discharge plasma led to acidic solutions with excellent and broad antibacterial activity. Because PAW caused severe membrane damages in bacteria and diffused freely in extracellular matrix, PAW also demonstrated good anti-biofilm activity. However, further studies revealed that trace amounts of metal ions (mainly copper and zinc) in PAW brought by plasma treatment played key roles in bacteria inactivation. The contribution of metal ions to the antibacterial activity varied among PAWs from different working gases. However, solution acidification caused by reactive species in plasma was essential. The experimental results demonstrated that potential artifacts in reported biological activities of PAWs should be considered.

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A semi-relativistic variant of the sw-Xa method is derived. Its foundation from the fully relativistic treatment is shown. All the relativistic shift effects, direct (Darwin term, mass-velocity term) as well as indirect effects (via the potential) are considered. Spin-orbit coupling is omitted. The method is equivalent to the semi-relativistic method of Wood and Boring but simpler in numerical realisation. The computational effort is only slightly increased compared with the non-relativistic sw-Xa scheme. Results for the uranium atom and I, and C2 mo!ecules are reported and compared with results from fully relativistic calculations. t Present address: Zentralinstitut fur Kernforschung, Akademie der Wissenschaften der DDR, Dresden, German Democratic Republic.