Subcritical butane technology was employed for the separation of abamectin on the fresh tea leaves surface.Under the conditions of solid-liquid ratio of 1∶10 (m/V), the experiment was designed via the response surface methodology and conducted at different temperature, various separation time and discrepant cycle number.Besides, the activity of the polyphenol oxidase (PPO) relating to the quality of the tea was determined and compared.At the same time, scanning electron microscopy (SEM) was used to observe the surface structure of fresh tea leaves before and after treatment, and the effect on physiological characteristics of the leaves by subcritical butane treatment was analyzed.The experimental results showed that the subcritical butane extraction could effectively isolate the abamectin, making the physical structure basically remained and the polyphenol oxidase activity preserved as well.Through the analysis by Design Expert software, the optimal processing parameters of separating abamectin were as follows: 45℃, 30 min, 1 cycle, and solid-liquid ratio of 1∶10 (m/V).Under the optimal conditions, the separation efficiency was over 91% and the relative PPO activity was 25.73%.The structure of fresh tea leaves changed insignificantly before and after the butane processing.This study suggested that the subcritical butane extraction technology could effectively remove pesticide residues in tea, thus provided a certain scientific basis for application of subcritical fluid removal of pesticide residue in natural plants.

Objective : To study root morphology, the incidence of three root canals and the root canal anatomy of maxillary premolars. Methods: The cone-beam computed tomography (CBCT) data of 779 maxillary first premolars and 728 maxillary second premolars were collected from 412 patients in Zhuhai Stomatological Hospital. The root and canal morphology, incidence of three canals, bilateral symmetry and location of root canal bifurcation were analyzed. Results : The incidence of three canals in the maxillary first premolars was 1.8% and that in the maxillary second premolars was 0.3%. The incidence of three canals in the maxillary first premolars was significantly higher than that in the maxillary second premolars (c2=8.304, P=0.004). The symmetrical ratio of the three-canal maxillary first premolar was 27.3%. There was no symmetrical three-canal maxillary second premolar. The anatomical morphology of the maxillary premolar can be single root, double root or trident root. Its internal root canal system is complex and diverse. There are seven kinds of Vertucci morphology: the first maxillary premolar is mainly Vertucci IV type, and the second maxillary premolar is mainly Vertucci I type. Most of the root canal bifurcations of the three-canal maxillary premolars were observed in the midthird or the cervical third of the root. All three-canal maxillary premolars had three independent apical foramens. Conclusion The root canal morphology of maxillary premolars is complex and changeable. CBCT plays an important role in the discovery of variation and extra root canals.

Objective:To investigate the clinical, endoscopic and pathologic characteristics of gastric hyperplastic polyps coexisting with gastric cancers.Methods:A retrospective study was performed involving 18 patients who were pathologically confirmed with gastric hyperplastic polyps coexisting with gastric cancers. The clinical features, endoscopic findings, pathological characteristics and treatment strategy were analyzed.Results:The age of 18 patients was 67. 2±7. 8 years (ranged 45-79), including 6 males and 12 females. The symptoms included abdominal pain, distention, and some patients were asymptomatic. Multiple polyps (13/18) were common. Single lesions were often located in the gastric corpus (7/18). Endoscopy showed various morphological changes. Pedunculated polyp was the most common type (15/18). All polyps were larger than 10 mm in diameter, and the polyps in 9 patients were larger than 20 mm. Fourteen patients had atrophic gastritis in the background mucosa, and 4 patients had Helicobacter pylori ( HP) infection. Conclusion:Gastric hyperplastic polyps coexisting with gastric cancers shows no specific symptoms. For HP (-) atrophic gastritis patients accompanied with multiple gastric polyps, malignant transformation of those larger and pedunculated polyps is of possibility.