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Objective Tostudy the influence of pipe structures on the mixing uniformity of airborne effluents from nuclear power plant chimneys. Methods We used the computational fluid dynamics (CFD) method to simulate the velocity distribution and gas mixing in long straight pipes (I type) with square section and circular section, 90° single-bend pipes (L type) with square section and circular section, and 90° double-bend pipes (S type and U type) with square section and circular section. Results For the long straight pipe, due to the lack of flow disturbance caused by structural changes, the mixing effect was not good; when the pipe section was circular, it might take mixing distance 20 times the hydraulic diameter to achieve the uniformity index required by the relevant standard; for the square pipe, the distance might be longer. In the single bend pipe with square section, the velocity uniformity was improved more greatly after the bend, and the tracer gas met the mixing uniformity at a shorter distance (11 times the hydraulic diameter), as compared with the single bend pipe with circular section. For the S-type double-bend pipe, the tracer gas appeared uniformly mixed after a distance 6 times the hydraulic diameter in the square pipe, and 7 times the hydraulic diameter in the circular pipe. For the U-type double-bend pipe, the gas in the square pipe also achieved uniform mixing ata shorter distance downstream, and the airflow showed greater disturbance when passing through the bend. Conclusion The CFD method can make an accurate prediction for the change patterns of gas mixing uniformity in pipes with different structures, and can partially replace physical experiments to study the factors affecting the mixing uniformity of airborne effluents from the chimney of nuclear power plants.
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Objective To optimize extraction process of flavonoids from Toosendan Fructus.Methods Three parameters that significantly affect the extraction rate of flavonoids, ratio of material to water, extraction time and ethanol concentration, were taken into consideration for extraction ratio of flavonoids from Toosendan Fructus. Based on the results of single-factor experiment, the extraction parameters of flavonoids from Toosendan Fructus were optimized by Box-Behnken of response surface methodology (RSM).Results The optimum extraction conditions were as follow: material to water ratio was 1:35; extraction time should be 3 h; ethanol concentration was 70%. The extraction ratio was up to 0.587 3% in the optimum extraction conditions.Conclusion The actual value is highly matching the theoretically value of RSM model. The results indicated that this method can rationally optimize extraction process of flavonoids from Toosendan Fructus.
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Objective To observe the prevention and treatment of the total flavonoids from Litchi chinensis Sonn( TFL) on hepatic fibrosis induced by dimethylnitrosamine(DMN)in rats, and to explore its mechanism. Methods Ninety SD rats were randomly divided into six groups, normal control group, model control group, colchicine group, high-, medium- and low-dose TFL group(n=15).Expect for normal control group, the other groups were given intraperitoneal injection of 2 mL.kg-1 of 5% dimethylnitrosamine for 4 weeks as the model group. The rats in the normal control group and model control group were given 5 mL.kg-1of 0.9% sodium chloride solution, colchicine group was treated with 0.1 mg.kg-1 colchicine.High-, medium-and low-dose TFL groups were given 200, 100 and 50 mg.kg-1 of TFL.The rats were sacrificed and the livers were harvested and stained with HE and Masson staining to observe pathological changes and liver fibrosis in the same part 6 weeks after all the medicine was given to the rats each day. Immunohistochemistry and Western blotting were used to detect the expression of the transforming growth factor β-Ⅰ/type Ⅱ receptor ( TβRⅠ/Ⅱ) , collagen Ⅰ( Col Ⅰ) and Ⅲ collagen ( Col Ⅲ) . Results Compared with the normal control group, the semiquantitative score of liver fiber and the protein expression of TβRⅠ, TβRⅡ, ColⅠ and Col Ⅲ in the model control group were significantly increased(P<0.01).Compared with the model control group, the protein expression levels of TβR, TβRⅡ, ColⅠand ColⅢwere significantly decreased( P<0.01) in the high-,medium-and low-dose TFL group.The semiquantitative score of liver fiber was significantly decreased( P<0.01) with a dose-effect relationship. Conclusion TFL can inhibit formation of DMN-induced liver fibrosis in rats, which may be related with reduction of expression of TβRⅠ/Ⅱ of hepatic fibrosis promoting factor TGF-β1 , inhibition of the activation and increase of hepatic stellate cells, reduction of the collagen content.
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Objective To study the effect of using handhold magnifier on reading speed in patients with low vision and normal-sighted people. Design Prospective,control study. Participants Low vision (13 patients)and normal-sighted readers (37 persons) who use handhold magnifiers or the first time. Method Nine-point text was read by normal vision subjects without magnifier and then with two magnifiers with different magnification (+10 D,+20 D) in different eye-to-magnifier distance (10 cm,35 cm). Nine-point text was also read by low vision people with magnifiers. The big printed text under the same magnification without magnifier was also read by low vision group. Reading speed was recorded. Main Outcome Measures Reading speed (words per minute). Result For normal vision subjects,reading speed without magnifier (194.6?45.2 words/min) is faster than that with a 10D magnifier in an eye-to-magnifier distance of 10cm (159.7?44.7 words/min) (P=0.001),and distance of 35cm (162.5?46.7words/min) (P=0.002),respectively. Reading speed without magnifier is also faster than that with a 20D magnifier in an eye-to-magnifier distance of 10cm (150.3?43.3 words/min) (P
