Particle-in-Cell/Monte Carlo simulation of CF4 discharge in capacitively coupled plasma reactor
We present the structures of the CF4 radio-frequency discharge between parallel electrodes using the Particle-in-Cell/ Monte Carlo method. The simulation takes into account four types of charged species, CF3 , CF − 3 , F − ions, and electrons. The cross-sections of electron-CF4 collision processes are based on the paper of Kurihara et al. [1]. Positive–negative ion recombination which plays an important role in the charged particle balance is also considered in the model using method proposed by Nanbu and Denpoh [2]. The structure of the CF4 discharge is typically electronegative discharge and is characterized by the presence of negative ions (F− and CF3 ), which are the dominant negative charged species (see Fig. 1(a)). The electron density profile and electric field at phase in a rf period are shown in Fig. 1. The local maxima of the electron density is significant feature of electronegative discharges, which cannot be observed in electropositive discharges. Moreover, we can observe the double-layer structure (i.e. the local maxima or minima of the electric field) and the field reversal near the bulk-sheath interface. Historically, the double layer phenomena were first described experimentally and theoretically in rf glow SiH4 discharge by T. Makabe et al. [3]. In conclusion, the abundance of negative ions is one of the main features in the discharges and this profoundly influences the sheath dynamics such as electric field reversal, double layer structure and local maxima of electron density.
Monte Carlo Collision Simulation of Positive-Negative Ion Recombination for a Given Rate Constant
Here is proposed the Monte Carlo collision simulation method for the positive-negative ion recombination whose rate constant is given as a function of temperature. The method makes it possible to simulate a nonequilibrium state of ions in electric discharges.
Thorium-induced Anatomical and Histopathological Changes in Liver of Swiss Mice
ObjectivePresent study is aimed to investigate the anatomical and histopathological changes in liver tissues of Swiss albino male mice, one month after intravenous administration of thorium (232Th; 4 and 40 mg/kg).MethodsSynchrotron X-ray micro-CT imaging, CD31 immuno-cytochemistry, hematoxylin & eosin staining and Periodic acid-Schiff staining were performed to study changes in liver anatomy, blood vessels/capillaries, histology and glycogen content of liver, respectively.ResultsSynchrotron X-ray micro-CT imaging of liver showed loss of blood vessels in mice treated with thorium (4 mg/kg), which was more prominent at higher dose of thorium (40 mg/kg). These thorium-induced changes in liver were correlated with the decrease in CD31 positive cells and loss of tissue architecture. A dose-dependent increase in glycogen content was also observed in the liver of thorium-treated mice.ConclusionOur results provide novel insight about the effects of thorium on liver, which may have significant implications in understanding the mechanism of thorium thorium-induced hepatotoxicity.