With the intensive application of sulfonamides in aquaculture and animal husbandry and the increase of sulfonamides discharged into the environments, there is an increasing need to find a way to remediate sulfonamidecontaminated environments. Two bacterial strains capable of degrading sulfonamides, HS21 and HS51, were isolated from marine environments. HS21 and HS51 were identified as members of Escherichia sp. and Acinetobacter sp., respectively, based on 16S rRNA gene sequencing. Degradation of each sulfonamide by Escherichia sp. HS21 and Acinetobacter sp. HS51 was characterized using capillary electrophoresis. About 66 or 72% of sulfapyridine and 45 or 67% of sulfathiazole contained in the media was degraded by Escherichia sp. HS21 or Acinetobacter sp. HS51, respectively, after incubation for 2 days. The supernatant from culture of Escherichia sp. HS21 or Acinetobacter sp. HS51 grown in sulfapyridine or sulfathiazole contained media had much attenuated cytotoxicity against HeLa cells. These results suggest that Escherichia sp. HS21 and Acinetobacter sp. HS51 are new bacterial resources for biodegrading sulfonamides and indicate the potential of isolated strains for the bioremediation of sulfonamide-polluted environments.

A one-dimensional fluid/Monte Carlo hybrid model was used to quantitatively study the secondary electron effect on sustaining the discharge by examining the ionization induced by bulk electrons and secondary electrons under different external discharge parameters. The results indicate that as the voltage increases, secondary electrons gain more energy from the stronger electric field. Therefore, the ionization region induced by secondary electrons expands and the ionization rate becomes comparable to and even exceeds that of bulk electrons. As the pressure increases, secondary electrons collide with neutrals sufficiently, thus their contribution to the plasma generation becomes pronounced and eventually they dominate the discharge. Besides, the distribution of the secondary electron ionization rate varies from flat to saddle-shape, due to the energy loss at the discharge center at higher pressures. Finally, when the discharge gap expands, the electron density calculated in the case without secondary electrons increases linearly, whereas the value first increases and then decreases in the model with secondary electrons taken into account. The results obtained in this work are important for improving the high aspect ratio etching process by secondary electrons.

In this work, the electron power absorption mode transition in capacitively coupled Ar/CF4discharges is investigated by using a one-dimensional fluid/electron Monte Carlo hybrid model. Different electron power absorption modes are observed under various external discharge conditions, which could be explained by examining the contribution of bulk electrons and secondary electrons respectively. The results indicate that as the gap increases, the electron power absorption mode changes from the drift-ambipolar (DA) mode to a α-γ-DA hybrid mode. This is ascribed to the enhanced ionization process of secondary electrons due to their sufficient collisions when the discharge region expands, as well as the weakened drift and ambipolar electric fields. By increasing the secondary electron emission (SEE) coefficient, the number density of secondary electrons grows, and thus the discharge experiences a transition from a α-DA hybrid mode over a α γ- -DA hybrid mode and finally into the γmode. Moreover, when the proportion of CF4 increases, the discharge tends to be more electronegative. As a consequence, the discharge gradually transits from a α-γ hybrid mode over a α- -DA hybrid mode, and finally to the DA mode.γ