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Magnetic fields are safe and used in noninvasive physical therapies. Numerous studies have confirmed that magnetic fields have good osteogenic effects and certain value for clinical application in accelerating orthodontic tooth movement, promoting bone-implant integration, promoting fracture healing and improving the effects of distraction osteogenesis. Magnetic fields are expected to become applied as effective auxiliary methods for treating oral diseases. To support the clinical application of magnetic fields, this article reviews the applications of magnetic fields in the oral cavity, the biological effects on bone cells and the molecular mechanisms through which magnetic fields regulate bone metabolism. The biological effects of magnetic fields on bone cells include promoting osteogenesis by osteoblasts and mesenchymal stem cells and inhibiting bone resorption by osteoclasts. At the molecular level, bone cells sense and respond to magnetic stimulation, and through various mechanisms, such as displacement currents, Lorentz forces, and free radical pair effects, stimuli are transformed into biologically recognizable electrical signals that activate complex downstream signaling pathways, such as the P2 purinergic receptor signaling pathway, adenosine receptor signaling pathway, transforming growth factor-β receptor signaling pathway, mammalian target of rapamycin (mTOR) pathway, and Notch pathway. In addition, magnetic parameters, which are the factors affecting the osteogenic effects of magnetic fields, are discussed. However, the mechanisms of the osteogenic effects of magnetic fields are unclear, and further studies of these mechanisms could provide effective strategies for bone regeneration and periodontal tissue regeneration. In addition, considering the target of magnetic field therapies, combination with other drugs could lead to new strategies for the treatment of oral diseases.

Rainfall-runoff is the main source of pollution in the urban water environment. This study investigated the dynamic changes of soluble Nickel (Ni) and Arsenic (As) in the receiving water body after the rainfall and runoff of the Meishe River in Haikou. Field sampling and indoor analysis were used. Results revealed that the solid-liquid partitioning of Ni and As in the receiving water body is directly disturbed by the inflow of rainfall-runoff. The main source of the input is the suspended state, and the input of the dissolved state is smaller. The specific performance is as follows. Before the rainfall-runoff flows into the receiving water body, the ratio of soluble Ni and As to the total content reaches 55.67% and 94.77%, respectively. After the rainfall-runoff flows in, a series of dynamic changes of Ni and As occur in the receiving water body. The proportion of soluble Ni and As at the outlet decreases significantly and changes dramatically, reaching 20.97% and 76.92% of the total content, respectively. The proportion of soluble Ni and As in the downstream of the drainage outlet also decreases to a certain extent, reaching 47.23% and 88.38%, respectively. The data under different rainfall scenarios indicate that the long dry period, when the rainfall is less than 10 mm, is the main factor affecting the dynamic changes of soluble Ni and As. Furthermore, the long dry period, along with the peak time, and magnitude of the rain intensity are the major influencing factors of the response time and degree of soluble Ni and As to rainfall-runoff, when the rainfall amount ranges from 10-30 mm. The peak time of rainfall intensity is the main factor affecting the dynamic change of soluble Ni and As in the receiving waters when the rainfall amount is above 30 mm. The effects of rainfall-runoff on the soluble Ni and As in the receiving water are different. When the dry period is short and the maximum rainfall intensity is high, in receiving water, soluble As is less affected by rainfall-runoff, while soluble Ni is significantly affected.

Rubber-like materials are widely used in mechanical systems. Schallamach waves appear in friction process due to their small elastic modulus and relatively large surface adhesion energy, which may cause some negative influences, such as additional vibration and singular wear. In-depth researches into the characteristics and mechanism of Schallamach waves are of great significance to development and application of rubber-like materials. Therefore, the nucleation and propagation law of Schallamach waves are investigated by using in-situ experiments and 3D finite element simulation method. Results indicate that small wrinkles appear firstly at the edges of contact regions. Here, the small wrinkles propagate towards the centers of the contact regions in a spiral manner, which is analyzed by using elastic theory. The first Schallamch wave forms on the sides of the contact region, while the subsequent waves nucleate at the front of the contact region. Then, In-situ experiments are carried out to study the influences of materials ratios and sliding velocity on the behaviors of Schallamach waves. Based on the finite element model, analysis results reveal the law of propagation speed, wave length and wave amplitude of Schallamach waves, and the relationship between contact area and force (frictional and vertical force). There is basically no sliding exiting in the contact interface during friction process, and in some extent the Schallamach waves play a lubricating role.