Electric current pulse (ECP) was commonly applied to solidification process of Al melt to achieve fine solidification microstructure. In this paper, numerical simulation method was employed to analyse flow behaviour of the melt and the mechanism of ECP on the grain refinement during the solidification. The calculation results showed that the ECP led to fluctuation of the Al liquid surface, and the liquid flowed inward and down in a circular motion. The fluctuation and circular flow behaviour were caused by the forces including Lorentz force, surface tension and buoyancy. The results also revealed that the higher the frequency and peak value of the ECP, the larger the flow velocity was. On the other hand, the depth of the electrodes in the liquid had little influence on the convection flow of the liquid. In summary, our simulation results explained the refinement mechanism of the ECP on solidification microstructure and provided a novel and feasible approach to evaluate and optimise the structure refinement of the ECP.
Whether the regression of gastric metaplasia in the duodenum can be achieved after eradication of Helicobacter pylori is not clear. The aim of the present study was to investigate the relationship between H. pylori infection and gastric metaplasia in patients with endoscopic diffuse nodular duodenitis. Eighty-six patients with endoscopically confirmed nodular duodenitis and 40 control patients with normal duodenal appearance were investigated. The H. pylori-positive patients with duodenitis received anti-H. pylori triple therapy (20 mg omeprazole plus 250 mg clarithromycin and 400 mg metronidazole, all twice daily) for one week. A control endoscopy was performed 6 months after H. pylori treatment. The H. pylori-negative patients with duodenitis received 20 mg omeprazole once daily for 6 months and a control endoscopy was performed 2 weeks after treatment. The prevalence of H. pylori infection was 58.1%, and the prevalence of gastric metaplasia was 57.0%. Seventy-six patients underwent endoscopy again. No influence on the endoscopic appearance of nodular duodenitis was found after eradication of H. pylori or acid suppression therapy. However, gastric metaplasia significantly decreased and complete regression was achieved in 15/28 patients (53.6%) 6 months after eradication of H. pylori, accompanied by significant improvement of other histological alterations. Only mild chronic inflammation, but not gastric metaplasia, was found in the control group, none with H. pylori infection in the duodenal bulb. Therefore, H. pylori infection is related to the extent of gastric metaplasia in the duodenum, but not to the presence of diffuse nodular duodenitis.
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