Inactivation of Staphylococcus aureus by the synergistic action of charged and reactive plasma particles

In this paper, a low-pressure capacitively coupled plasma discharge sustained in an argonoxygen mixture was studied in order to evaluate its properties in terms of inactivation of Staphylococcus aureus. The plasma parameters as electron temperature and plasma density were measured by the Langmuir probe (N_e ≈ 10¹⁵ m⁻³, T_e ≈ 1.5 eV), while the neutral atom density was in the range of 10²¹ m⁻³. In the plasma phase, oxygen radicals were taken as reference of the reactive species with antimicrobial activity, and oxygen spectral lines, over a range of plasma process parameters, were investigated by the optical emission spectroscopy. Optimal plasma conditions were found, and a count reduction of 4 log in a few minutes of the bacterium proves the potentiality of an industrial grade plasma reactor as a sterilization agent.     

Plasma cleaning technique for the removal of mixed materials

Erosion of materials by physical sputtering is the most fundamental of plasma–surface interactions in tokamaks. Carbon and tungsten materials planned to be used in ITER divertor are subjected to erosion, which produces local redeposition of mixed layers. Tritium retention in mixed materials is the major concern due to the limits imposed for safety reason by nuclear licensing. No technique has yet been proven capable of remove trapped tritium in ITER operating environment. In-situ oxidative cleaning techniques have been developed to remove co-deposits. Since oxygen can be incompatible with Be first wall (getter effect), a plasma cleaning using hydrogen–argon gas mixture has been proposed in this work. C–W mixed materials were produced for this purpose by capacitively coupled RF plasma sputtering. The process has been investigated by optical emission spectroscopy and Langmuir probe.     

Characterization by optical emission spectroscopy of an oxygen plasma used for improving PET wettability

Polymers have excellent bulk physical and chemical properties but usually poor surface properties. For wettability improvement plasma technology is one of the most promising techniques. Several studies about surface modifications of polyethylene terephthalate (PET) exposed to an oxygen plasma have been already carried out. In this work an analysis of the plasma phase by optical emission spectroscopy (OES) has been employed in order to establish a correlation with the surface effects induced by plasma exposition on PET chemical composition and wettability, investigated by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. The treatment has been carried out for a time of 60 s at a constant pressure (15 Pa) and at different process powers ranging from 20 to 200 W. As expected, the best performance has been obtained at a power of 200 W due to the larger presence of oxygen radicals (OI) with the assistance of ionic species (OII, O₂⁺) which create dangling bonds on the substrate surface.     

Effect of Assay Temperature on Activity of Citrus Pectinesterase In Fresh Orange Juice

The effect of temperature on pectinesterase activity in crude enzyme extract from Valencia pulp was determined. The effect is best described by the regression equation: LN PEU = 14.3446 ?3415 (1/T) with a correlation coefficient of 0.991. The activation energy was determined to be 28,392 joules/mol. This regression equation was used to predict the enzyme activities of different juice samples and verified by assay of Valencia juice at various temperatures. Duncan analysis indicated no significant differences in the predicted pectinesterase activities of the concentration-corrected crude extract and collective means of the Valencia juices at the respective temperature.     

Solubilization of Cell Wall Bound, Thermostable Pectinesterase from Valencia Orange

Complete solubilization of citrus pectinesterase is not effected by alkaline salt buffers but is partially enhanced after degradation of the cell wall by pectinase and cellulase. After heating at 70°C for 2 min, the pectinesterase fractions solubilized after enzymatic cell wall degradation possessed three times the residual activity of the pectinesterase fractions solubilized by alkaline salt buffer. Isoelectric focusing prints of pectinesterase activity and SDS polyacrylamide gel electrophoresis suggest increased solubilization of a heat stable pectinesterase isozyme after cell wall degradation.