The electrospinning of stereocomplex nanofibers of high-molecular-weight poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) (PLLA/PDLA = 1:1) was carried out with chloroform as the spinning solvent. The stereocomplex nanofibers with diameters of 830-1400 and 400-970 nm were successfully obtained at voltages of -12 and -25 kV, respectively. Wide-angle X-ray scattering indicated that with an increasing absolute value of voltage from 0 to 25 kV the crystallinity of homo-crystallites composed of either PLLA or PDLA decreased from 5% to 1%, whereas the crystallinity of stereocomplex crystallites increased slightly from 16% to 20%. The obtained results reveal that electrospinning is an effective method to prepare stereocomplex nanofibers with a negligibly small amount of homo-crystallites, even when high-molecular-weight PLLA and PDLA are used, and that the orientation caused by high voltage (or electrically induced high shearing force) during electrospinning enhances the formation and growth of stereocomplex crystallites and suppresses the formation of homo-crystallites.

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Inactivation mechanisms of plasma treated microorganisms are still major subjects. We have developed a biological assay which evaluates in vivo DNA damage of the viruses treated with non‐thermal atmospheric pressure plasma in air. Different doses of the plasma were applied to wet state of λ phage particles under neutral pH and near the room temperature. From each sample of treated λ phages, DNA was purified and subjected to in vitro DNA packaging reactions. Survival curves of the re‐packaged phages showed an extremely large D value (D = 25 s) compared to the previous D value (D = 3 s) obtained from the survival curves of the treated phages. The results indicate the evidence that DNA damage hardly contributed to the inactivation.

The physical processes and chemical reactions that take place inside different temperature plasma zones in water are only partially understood. The present study uses the emission spectroscopy and hydrogen peroxide measurements as indicators of the processes that take place on the gas-liquid boundary and inside plasma. Based on the hydrogen peroxide measurements with negative and positive high-voltage polarities as a function of solution conductivity, it was concluded that the main difference between positive polarity plasma and negative polarity plasma lies in the active radical concentration inside plasma. Data suggested that in the positive polarity electrical discharge the hydrogen peroxide concentration depends on the solution pH, whereas in the negative polarity discharge, it depends on the solution conductivity. Also, only in the negative polarity discharge do some of the electrons that are emitted from the high voltage electrode diffuse into the bulk where they react with the solutes.