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The tower foundation is an important component of the tower grounding device. The conditions in permafrost areas are relatively harsh, and damage to the foundation can affect the grounding performance of the grounding device. However, the damage characteristics of permafrost to the tower foundation in permafrost areas are not yet clear, and effective protection of the foundation cannot be achieved. Based on this, this article constructs a simulated frozen soil experimental platform through experiments, replacing the tower foundation with concrete specimens. The electrical and mechanical properties after freeze-thaw were measured using the quadrupole method and resonance method, respectively. The self performance of the tower foundation under different moisture content freeze-thaw conditions was studied, and the performance change law of the tower foundation after freeze-thaw was obtained to explore the damage of frozen soil to the tower foundation in frozen soil areas. It can be considered that the frozen soil in permafrost areas does not cause significant damage to the tower foundation itself in a limited number of years.

Objective To investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the viability, proliferation, differentiation and apoptosis of cultured chondrocytes and ex vivo development of embryonic mouse metatarsals. Methods Chondrocytes isolated from neonatal mice (3-5 days old) and metatarsals from mouse embryos (18 days of gestation) were both divided into control group and 3 LIPUS treatment groups for LIPUS exposures with acoustic intensity and duty ratio combinations of 30 mW/cm2-20% (LIPUS Ⅰ), 30 mW/cm2-40% (LIPUS Ⅱ), and 50 mW/cm2-20% (LIPUS Ⅲ); all the other ultrasound parameters were identical (central frequency of 1.5 MHz, repetition frequency of 1 kHz and exposure time of 20 min per day). After LIPUS treatments, the chondrocytes were examined for changes in cell viability, proliferation and apoptosis using cell counting kit-8, EdU assay and TUNEL assay, respectively. The mRNA expression levels of cartilage matrix-related genes were examined by qRT-PCR. The changes in the total length and cartilage length of the metatarsals were measured after the treatments. Results Exposure to LIPUS significantly enhanced the viability and proliferation and reduced the apoptotic rate of the chondrocytes, and the effect was the most obvious in LIPUS Ⅱ group. LIPUS treatment significantly up-regulated the mRNA expressions of Col Ⅱ and proteoglycan and reduced the mRNA expression of Col X in the chondrocytes (P < 0.05). As for the metatarsals, the growth rates of the total length and cartilage length were significantly greater in LIPUS Ⅱ and LIPUS Ⅲ groups than in the control group (P < 0.001), but no significant difference was found between LIPUS Ⅰ group and control group. Conclusion LIPUS treatment can promote bone growth by stimulating chondrocyte proliferation and extracellular matrix synthesis while inhibiting cell apoptosis. These effects are related with the acoustic parameters of LIPUS, and the parameter setting with an acoustic intensity of 30 mW/cm2 and a duty ratio of 40% can be optimal for LIPUS treatment.

Objective To observe the developmental process of murine meniscus after birth and investigate the expression patterns of 3 types of fibroblast growth factor receptors (FGFRs) during this process. Methods Mice at different ages (1 d old and 1, 2, 4, 6 and 12 weeks old) were sacrificed and the knee joints were harvested and embedded in paraffin. The sagittal sections of knee joint were stained with Safranin O-fast green to observe the structure of murine meniscus. The expression of type Ⅰ collagen, type Ⅱ collagen, and 3 types of FGFRs were detected by immunohistochemistry. Results At birth, the meniscus exhibited distinguishable inner and outer regions, with proteoglycan of darker staining rich in the inner region, while the outer region lightly stained. At 1-week age, the inner-outer region was more obvious, and the inner region mainly expressed type Ⅱ collagen, while the outer region expressed type Ⅰ collagen. At 2 weeks, some cells in the anterior horn became hypertrophied, and the hypertrophy was further aggravated at 4 weeks of age. By 6 weeks, ossification tissues were observed in the anterior horn of the meniscus. At 12 weeks, the meniscal developmental process after birth was basically completed, and mineralized structure resembling bone marrow cavity was found in the anterior horn. The expression of the 3 types of FGFRs had similar spatiotemporal pattern which reached a peak at 1~2 weeks of age and then gradually decreased (P < 0.05) with its spatial distribution changing from a uniform distribution to an edged distribution in the inner zone of anterior horn. However, the expression of FGFRs in the posterior horn had no obvious changes. Conclusion During the postnatal development of murine meniscus, the cartilage matrix, collagen distribution and expression patterns of 3 types of FGFRs have spatiotemporal specificity, which suggest that FGFRs play an important role in the meniscal development.

In recent years, as a new visible light responsive nonmetal photocatalyst, graphite-phase carbon nitride (g-C3 N4) has been widely used for organic pollutants removal in photocatalysis system due to its suitable band gap width characteristic, enough active sites and low cost. However, the drawback of its low visible-light utilization and fast recombination of photogenerated electron-hole pairs that play negative effect on its photocatalytic activity. Combine with the nonmetal properties of g-C3 N4, nonmetal doping is an effective strategy to further improve the photocatalytic performance of g-C3 N4, and has attracted more and more attention on photocatalysis. In this paper, the common preparation methods of non metal doped g-C3 N4 composite materials are introduced. In addition, the research progress of different nonmetal doped g-C3 N4 applied in photocatalytic degradation of organic pollutants is summarized in detail, and its mechanism of photocatalytic degradation of organic pollutants under visible light is also discussed. Finally, the challenges and suggestions for the photocatalytic degradation of organic pollutants in water by nonmetal doped g-C3 N4 are proposed, and this review also helps to provide insights into the removal of organic pollutants by nonmetal doped g-C3 N4 coupled photocatalysis. [ABSTRACT FROM AUTHOR]