ABSTRACT
This experiment measured the instantaneous temperature and velocity field synchronously in non-isothermal turbulent boundary layer in a rotating straight channel with a parallel-array hot-wire probe. The Reynolds number based on the bulk mean velocity (U) and hydraulic diameter (D) is 19000, and the rotation numbers are 0, 0.07, 0.14, 0.21 and 0.28. The mean velocity u and mean temperature T as well as their fluctuating quantity u' and T' were measured at three streamwise locations (x/D = 4.06, 5.31, 6.56). A method for temperature-changing calibration with constant temperature hot-wire anemometers was proposed. It achieved the calibration in operational temperature range (15.5 °C-50 °C) of the hot-wire via a home-made heating section. The measurement system can obtain the velocity and temperature in a non-isothermal turbulent boundary layer at rotating conditions. The result analysis mainly contains the dimensionless mean temperature, temperature fluctuation as well as its skewness and flatness and streamwise turbulent heat flux. For the trailing side, the rotation effect is more obvious, and makes the dimensionless temperature profiles lower than that under static conditions. The dimensionless streamwise heat flux shows a linear decrease trend in the boundary layer. It is hoped that this research can improve our understanding of the flow and heat transfer mechanism in the internal cooling passages of turbine rotor blades.
ABSTRACT
Objective:To explore the effects and the mechanism of metformin combined with celecoxib on the proliferation and apoptosis of hepatoma HepG2 and Huh7 cells.Methods:Hepatoma cells HepG2 and Huh7 were divided into control group, metformin group, celecoxib group and combination medication group, CCK-8 assay was used to detect cell proliferation; Hoechst33258 staining method was used to investigate the cell apoptosis; wound healing test was used to detect cells migration ability; Transwell invasion chamber test was used to detect cell invasion ability; Western blotting was used to detect the expression of AMPK, PI3K, Akt, mTOR.Results:After metformin and celecoxib treatment, HepG2 and Huh7 cells were gradually contracted, disintegrated and more apoptotic cells were noticed, and cell proliferation was significantly inhibited. The wound healing test results showed that the cell migration was significantly decreased ( P<0.05) under metformin and celecoxib treatment. The results of the transwell invasion chamber test showed that the metformin and celecoxib treatment inhibited the invasion of HepG2 and Huh7 cells ( P<0.05). The expression levels of AKT, AMPK, and mTOR were decreased in HepG2 cells in the combinational treatment group, and the expression level of PI3K was decreased and then increased; the expression levels of AKT, AMPK, PI3K, and mTOR in Huh7 cells were decreased. Conclusions:Metformin can cooperate with celecoxib to enhance the inhibitory effect on the proliferation, migration and invasion of HepG2 and Huh7 cells. The mechanism may be related to the inhibition of the expression of mTOR signaling pathway.
ABSTRACT
Objective To analyze the genotypes of Neisseria gonorrhoeae ( N. gonorrhoeae) epi-demic strains in Wenzhou, eastern China, and to study the mechanism of tetracycline resistance in these strains. Methods A total of 77 N. gonorrhoeae strains were isolated from patients with gonorrhea. Antimi-crobial susceptibility of these strains to penicillin, tetracycline, ciprofloxacin, spectinomycin, ceftriaxone and azithromycin was analyzed using E-test. PCR and DNA sequencing were used to detect the genes associ-ated with tetracycline resistance, such as Tet-M, mtrR promoter region and mtrR coding region. N. gonor-rhoeae multi-antigen sequence typing ( NG-MAST) and multilocus sequence typing ( MLST) were used to determine the molecular characteristics of all clinical isolates and tetracycline-resistant isolates, respectively. Results Among the 77 N. gonorrhoeae isolates, 74 (96. 10％), 27 (35. 06％) ,70 (90. 91％) and 15 (19. 48％) were resistant to penicillin, tetracycline, ciprofloxacin and azithromycin, respectively. All tested isolates were susceptible to spectinomycin and ceftriaxone. Nineteen isolates were resistant to tetracycline and all of them carried Tet-M gene. Among them, 17 had one deletion mutation of base A in mtrR promoter region and three had G45D mutation in mtrR coding region. NG-MAST classified the 19 tetracycline-resistant isolates into 11 different sequence types (ST). ST14781, ST1766 and ST1866 each accounted for 15. 79％(three strains). Two ST (10. 52％, 2/19) found in the present study had not been reported previously in the NG-MAST database. MLST showed the 19 tetracycline-resistant isolates belonged to 12 different STs, in which ST10899 accounted for 26. 32％ (five strains) and ST1600 accounted for 15. 79％ (three strains). Conclusions Mutations in mtrR promoter region and carrying Tet-M gene were associated with tetracycline resistance in N. gonorrhoeae. Clinical strains isolated in Wenzhou showed considerable molecular diversity. Measures should be implemented to monitor the spread of NG-MAST ST1766 and MLST ST1600 N. gonor-rhoeae clones with high resistance to tetracycline in Wenzhou.
