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Li Ma,Xin'an Wu,Yuhui Wei,Yan Zhou,Xiaohua Ma 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.11
The aim of this study was to investigate the effects of Pluronic F68 and Labrasol on the intestinal absorption and pharmacokinetics of rifampicin. Intestinal permeability of rifampicin with or without excipients was evaluated by an in situ single-pass perfusion method. A highperformance liquid chromatographic method was applied to study the pharmacokinetics of rifampicin with or without excipients. Labrasol or Pluronic F68 (0.1% and 0.05%, v/v), co-perfused with rifampicin (60 μg/mL), significantly increased in situ permeability. Similarly, verapamil (a typical P-gp inhibitor) also increased in situ permeability, but to a lesser extent. In vivo, the oral administration of rifampicin with or without Pluronic F68, Labrasol or verapamil resulted in statistically significant effect on t1/2 (4.83 to 7.75, 6.42 and 7.46 h) and total body clearance (0.46 to 0.26, 0.28, 0.24 L/h/kg). In addition, Pluronic F68, Labrasol and verapamil produced minor changes in AUC_0-t, which improved 1.55-, 1.54-, and 1.73-fold in comparison to control group, respectively. These results showed that Labrasol and Pluronic F68 might inhibit the function of P-gp in the intestine, thereby increasing intestinal absorption and changing the pharmacokinetic parameters of rifampicin. Therefore, excipient selection is an important factor to consider in rational formulation design.
Method to Estimate Lateral Earth Pressure on High-Filled Cut-and-Cover Tunnels
Li Ma,Sheng Li,I-Hsuan Ho,Qicai Wang,Bentian Yu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.3
High-filled cut-and-cover tunnels (HFCCTs) can be used in northwestern China to reclaim usable land. Because of the ultra-high backfill used in HFCCTs, the stress on the cut-and-cover tunnel (CCT) will change. However, The calculation method adopted at present for earth pressure usually result in either overestimation or underestimation. Different from vertical earth pressure, lateral earth pressure (LEP) can help stabilize the structure of HFCCTs. The current methods for estimating LEP rely mainly on Rankine’s theory or empirical formulas. Using conventional methods has led to errors between actual values and estimated values, and such deviation increases with an increase in the backfill height over the CCT. Due to the complex soil-arching effect, the current methods used for calculating LEP for HFCCTs need to be modified. These modifications need to consider characteristics of the CCT, mechanical properties of the backfill soil, and the geometry of the landform. In this work, several influential factors were identified through numerical analysis using the finite element method and propose four corresponding coefficients of modification: k0, the cross-sectional shape of the CCT; k1, the mechanical properties of the backfill; k2, the width of the CCT; and k3, the coupled effect of the slope angle and ratio of the width of the valley floor to the width of the CCT. Because current methods and specifications may overestimate the LEP for HFCCTs in valleys, a general equation was formulated for modifying the LEP coefficient. Also, this general modification equation was verified that agrees well with the numerical analysis results for different cases.