Excitation of nonlinear ion acoustic waves in CH plasmas

Excitation of nonlinear ion acoustic wave (IAW) by an external electric field is demonstrated by Vlasov simulation. The frequency calculated by the dispersion relation with no damping is verified much closer to the resonance frequency of the small-amplitude nonlinear IAW than that calculated by the linear dispersion relation. When the wave number $k\lambda_{De}$ increases, the linear Landau damping of the fast mode (its phase velocity is greater than any ion's thermal velocity) increases obviously in the region of $T_i/T_e < 0.2$ in which the fast mode is weakly damped mode. As a result, the deviation between the frequency calculated by the linear dispersion relation and that by the dispersion relation with no damping becomes larger with $k\lambda_{De}$ increasing. When $k\lambda_{De}$ is not large, such as $k\lambda_{De}=0.1, 0.3, 0.5$, the nonlinear IAW can be excited by the driver with the linear frequency of the modes. However, when $k\lambda_{De}$ is large, such as $k\lambda_{De}=0.7$, the linear frequency can not be applied to exciting the nonlinear IAW, while the frequency calculated by the dispersion relation with no damping can be applied to exciting the nonlinear IAW.Comment: 10 pages, 9 figures, Accepted by POP, Publication in August 1

Non-thermal Plasma - Nanometer TiO2 Photocatalysis for Formaldehyde Decomposition

In non-thermal plasma-nanometer TiO2 photocatalysis, the techniques of photocatalysis and plasma are combined, and do not need ultraviolet light. It can make use of some kinds of energy in the process of decomposing, while at the same time producing much free hydroxide and improving the efficiency of decomposing. It is regarded as one of the most promising technologies in air cleaning. A non-thermal plasma-nanometer TiO2 photocatalysis purifier was placed in a stimulant air conditioning room, followed by pumping in a mixture of formaldehyde and air. The purifier was then turned on to carry on the static state experiment of decomposing formaldehyde. The INTERSCAN4160 analysis instrument was adapted to analyze the variety of the formaldehyde density in the room. The fan was turned on in the room to keep the diffusion circulating in the room and alter the velocity of the air and the density for the experiment. The experiment shows that the efficiency of the decomposing formaldehyde in static state increased up to 90% after the Non-thermal Plasma-Nanometer TiO2 Photocatalysis process. In an air-conditioned room, the purifier can decrease the density of formaldehyde effectively. The concentration increasing effect of decomposing is more promising

Enhanced Steroid Metabolites Production by Resting Cell Phytosterol Bioconversion

The steroid metabolites 9-hydroxy-androstenedione (9-OH-AD), androstadienedione (ADD) and androstenedione (AD) are important steroidal pharmaceuticals. In order to raise the production of steroid metabolites, an efficient resting cell phytosterol bioconversion process was developed to produce 9-OH-AD in the presence of hydroxypropyl-β-cyclodextrin (HP-β-CD). Cell growth medium containing phytosterol as an inducer positively improved cell activity. Under aerobic conditions, bioconversion proceeded at 70 g L–1 phytosterol in the presence of HP-β-CD (the optimized molar ratio of HP-β-CD/phytosterol was 1:1) with 30 g L–1 resting Mycobacterium neoaurum NwIB-yV cells (cell dry mass) in a 5-L bioreactor, where 9-OH-AD production and space-time yield reached 36.4 g L–1 and 9.1 g L–1 d–1, respectively. The recycling of cells and HP-β-CD enables cost-saving and industrial applications. This bioprocess was also applied for the production of ADD and AD. The production of these steroid metabolites was much higher than that reported in previous studies