Stereoselectivity in drug metabolism can not only influence the pharmacological activities, tolerability, safety, and bioavailability of drugs directly, but also cause different kinds of drug–drug interactions. Thus, assessing stereoselectivity in drug metabolism is of great significance for pharmaceutical research and development (R&D) and rational use in clinic. Although there are various methods available for assessing stereoselectivity in drug metabolism, many of them have shortcomings. The indirect method of chromatographic methods can only be applicable to specific samples with functional groups to be derivatized or form complex with a chiral selector, while the direct method achieved by chiral stationary phases (CSPs) is expensive. As a detector of chromatographic methods, mass spectrometry (MS) is highly sensitive and specific, whereas the matrix interference is still a challenge to overcome. In addition, the use of nuclear magnetic resonance (NMR) and immunoassay in chiral analysis are worth noting. This review presents several typical examples of drug stereoselective metabolism and provides a literature-based evaluation on current chiral analytical techniques to show the significance and challenges of stereoselectivity assessing methods in drug metabolism.

Conventional metasurface carpet cloak generally has a narrow working bandwidth and a small incident angle range, which is far from meeting the requirements of modern military for broadband and wide-angle cloaking. Based on graphene apertures and graphene patches, we propose the design of metasurface carpet cloaks for terahertz wave and explore their application potential in realizing broadband and wide-angle cloaking. Simulation results demonstrate that the carpet cloaks based on graphene apertures and patches can achieve a large working bandwidth of 35.7% and 52.6%, and a wide angular span of  ±30° and  ±40°, respectively. The cloaking performance and the working bandwidths of the two graphene metasurface carpet cloaks can be tuned by changing the graphene Fermi energy uniformly. The carpet cloak constructed by graphene patches has a larger bandwidth and a wider angle domain than that by graphene apertures, which can be understood by comparing the phase dispersion of the two graphene metasurfaces.

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The hexagonal boron nitride (h-BN) nanosheets modified by silane coupling agent (KH560) were doped into acrylic acid coating on the surface of galvanized steel to improve its corrosion resistance. H-BN nanosheets modified by KH560 were prepared and characterised by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The corrosion resistance of the acrylic acid coatings was measured by electrochemical testing. The results show that the corrosion current density of the coating with modified h-BN nanosheets was reduced from 2.2 × 10−5 A/cm2 to 2.3 × 10−7 A/cm2 compared with the acrylic acid coating. The impedance of the composite coating with modified h-BN is 4435 Ω·cm2, higher than the BNNS coating (2500 Ω·cm2) and the acrylic acid coating (1500 Ω·cm2). This is due to the physical barrier and electrical insulation properties of the hexagonal boron nitride (h-BN) nanosheets.

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The development and utilization of underground space is an effective way to make intensive use of resources, solve "big city disease" and achieve high-quality development. The expansion and renovation of underground space in a central urban area is likely to cause serious damage to surrounding structures. In this study, a deep foundation excavation for the reconstruction of an urban subway station in the Greater Bay Area was chosen for analysis using the finite element method. Different from common excavation engineering, the interaction between the three coupling factors of train dynamic load, foundation excavation, and viaduct pile foundation were analyzed. Six different cases were calculated considering different working conditions of excavation depth and train dynamic load. Soil was evaluated using modified Cam-Clay model. The physical parameters of the soil were determined through on-site and laboratory tests. The results were compared with monitoring data, and the accuracy of the finite element model was verified. The settlement and influence range of the soil, and displacement and internal forces of viaduct piles were analyzed. The maximum settlement of the soil occurred in the direction of the short side of the foundation pit. The maximum value was approximately 0.53 times the excavation depth. The settlement increased by approximately 49% when applying the train load. The dynamic load had an aggravating influence on the horizontal displacement of the top of the pile, with a maximum increase of 51%. Moreover, the dynamic load increased the negative bending moment of the viaduct piles. This study provides a reference for the design and construction of geotechnical engineering projects.

Abstract. For the operating characteristics of limited capacity micro-grid, power quality disturbance impacting on the micro-grid is to be significantly larger than the civilian power grid, especially the transient power quality disturbances can not be ignored. By combining the advantage of wavelet transform and FFT (Fast Fourier Transform) respectively in the steady-state and transient power quality detection, a new method of power quality detection on limited capacity micro-grid is proposed. Firstly, limited capacity micro-grid model is established by MATLAB, then, the common micro-power system disturbance models are generated, finally, wavelet transform and FFT are combined to complete the detection and analysis of harmonic, and the detection and location of transient power quality disturbances. The simulation results show the effectiveness of the method which provides a new research idea for detection and location of power quality in limited capacity micro-grid.