The horizontal electric field from the lightning return-stroke channel is evaluated by the electromagnetic field equations of moving charges in this paper. When a lightning flash strikes the ground, the charges move upward the lightning channel at the return-stroke speed, thereby producing the electromagnetic fields. According to the electromagnetic field equations of moving charges, the detained charges, uniformly moving charges, and decelerating (or accelerating) charges in each segment of the channel generate electrostatic fields, velocity fields, and radiation fields, respectively. The horizontal component of the sum is the horizontal electric field over the perfectly conducting ground. For the real soil with finite conductivity, the Wait formula is used here for the evaluation of the horizontal electric field over the realistic soil. The proposed method can avoid the oscillation of the fields in the long distance by the FDTD method and the singularity problem of the integral equation by the Sommerfeld integral method. The influences of the return-stroke speed, distance, and soil conductivity on the horizontal electric field are also analyzed by the proposed method. The conclusions can be drawn that the horizontal electric field decreases with the increasing of the return-stroke speed; the negative offset increases with the increasing of horizontal distance and with the decreasing of the soil conductivity, thereby forming the bipolar waveform. These conclusions will be practically valuable for the protection of lightning-induced overvoltage on the transmission lines.

Studying underground propagation effects of lightning electromagnetic fields in different geological environments will contribute to more reasonable designs for protecting underground cables and electronic equipment. In this paper, we have analyzed influences of different geological environments, depths and soil water content on underground propagation of lightning electromagnetic fields in detail by using the finite difference time domain (FDTD) method in the 2-D cylindrical coordinate system to calculate components of underground electromagnetic fields at a horizontal distance of 200 m, including vertical electric field E z, horizontal electric field E r and azimuthal magnetic field H φ. The results show that the underground electric field is predominantly horizontal. Propagation of lightning electromagnetic fields in wet clay and wet limestone environment changes significantly compared to freshwater environment. Attenuation is larger with depth in wet clay and wet limestone, while propagation is unaffected in freshwater. When water content in soils ranges from 5% to 25%, the vertical electric field has the largest attenuation and the azimuthal magnetic field has the least attenuation. The electromagnetic fields in clay are most sensitive to changes in water content.

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Objective: To explain the anti-tumour effects of apatinib via the regulation of miRNA-21 in the PTEN/PI3K/AKT pathway. Methods: Measuring pathology, miRNA-21 and PTEN expression by H&E staining, in-situ hybridisation and immunohistochemistry in non-small-cell lung carcinoma (NSCLC). For the experiment, A549 cells were divided into four groups: apatinib, apatinib+blank, apatinib+miRNA and negative control. Cell proliferation, apoptosis, cell cycle, invasion and migration were assessed using the MTT, flow cytometry, transwell migration and wound-healing assays. Relative expressions of PTEN, PI3K, AKT, P21, MMP-2 and MMP-9 were evaluated using western blotting. Results: miRNA-21 and PTEN protein expressions of NSCLC tissues were found to significantly differ from those of adjacent normal tissues (P < 0.001). Compared with the control group, the cell apoptosis rate was significantly suppressed with increasing cell apoptosis in the G1 phase in the apatinib group (P < 0.001); the invasion A549 cell number and wound-healing rate were significantly depressed in the apatinib group compared with the control group (P < 0.001). However, A549 cell biological activities were significantly recovered with miRNA-21 transfection in the apatinib+miRNA group (P < 0.001). Western blotting revealed that PTEN and P21 expression in the apatinib group were significantly upregulated and that PI3K, AKT, MMP-2 and MMP-9 expression were significantly downregulated compared with the control (P < 0.001). miRNA-21 transfection led to significant suppression of PTEN and P21 expression and significant stimulation of PI3K, AKT, MMP-2 and MMP-9 expression (P < 0.001). Conclusion: Apatinib was proven to exhibit anti-tumour effects to NSCLC by regulating miRNA-21 via the PTEN/PI3K/AKT pathway.