Abstract:Patho-occlusion, which is characterized by the abnormalities of denture, jaw and craniofacial region, is an oral disease with high incidence in all countries. Orthodontics has been widely employed for the treatment of patho-occlusion, during which the nickel-titanium (NiTi) arch wires with shape memory and superelastic properties play a vital role. With the great development of manufacture technology and clinical applications, surface coatings such as titanium nitride (TiN) have been introduced onto the NiTi arch wires for lower frictional coefficient, better wear resistance and greater biocompatibility. In particular, physical vapor deposition (PVD) is the most common method for TiN coating, but the transformation temperature of target NiTi wires will be greatly affected during the conventional PVD process. Here in this study, the direct current bias of conventional PVD process was changed to pulsed negative bias for fabricating TiN coating, which could retain the shape memory and superelastic properties of target NiTi wires by avoiding temperature rise. Different TiN coated NiTi arch wires were prepared by adjusting the frequency and duty cycle of negative bias, and the morphology and transformation temperature of various samples were systematically investigated. The results reveal that the PVD process with lower frequency and duty cycle is more suitable for the preparation of TiN coated NiTi arch wires and better clinical applications can be anticipated.

Abstract:Using ideal magnetohydrodynamic equations, the magnetic component of geodesic acoustic mode was investigated analytically. It is found that the parallel component of the magnetic vector is on the same order of the poloidal component, which means the perpendicular projection of magnetic vector cannot be disregarded without any further consideration. It is shown that the radial magnetic vector is much less than the poloidal one and can be ignored directly.

Abstract:In this paper, atmospheric argon plasma was utilized to achieve surface cleaning and wettability modification of carbon fibers in aqueous solution. The morphology of fiber was characterized by scanning electron microscopy, surface chemical structure and composition were determined by fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and water contact angle and tensile strength were also tested. The results show that plasma treatment can not only remove the size and impurities on the fiber surface, but also maintain the original surface morphology, and introduce a large number of oxygen-containing polar groups. Further analysis indicates that fibers exhibit the best performance when they are treated with plasma for 120 s, and the water contact angle of fiber can be reduced to 45.1°. Moreover, little influence has been found for the plasma modification on the mechanical properties of fibers, and the tensile strength of carbon fiber can still be kept at 3.23 GPa after 300 s plasma treatment.

Abstract:Pulse transformer has the advantages of high step-up ratio, good reliability, small size and low price, and is widely used in high-voltage pulse circuits. However, when a semiconductor switch is used to drive a pulse transformer, an over-voltage may be generated due to the influence of the leakage inductance, which not only increases the loss but also may lead to overvoltage breakdown of the switch. In this paper, the mechanism of overvoltage generation was analyzed, the effects and disadvantages of conventional overvoltage suppression methods were compared, a new overvoltage suppression circuit was proposed, and the topology structure, working principle and circuit parameter selection basis were given. The effects of the new over-voltage suppression circuit were verified through modeling and simulation. Finally, the overvoltage suppression circuit was used to develop a compact heavy-duty high-voltage pulse generator which can generate pulses with 11 kV amplitude, 2 kHz frequency, and 2 μs pulse width, drive a load of floating electrode dielectric barrier discharge and generate stable low temperature plasma.

Abstract:In order to improve the resistance of tumor cells to chemotherapeutic drug, a method for sensitizing chemotherapy by promoting the cellular uptake of drugs has been developed. After cold atmospheric plasma treatment, reactive oxygen species in the medium increases significantly, further changing the permeability of cell membrane and allowing exogenous reactive oxygen species and calcium ions enter into cells. Meanwhile, changes in cell membrane permeability can increase cellular uptake of chemotherapeutic agents, and further increasing tumor cell killing efficiency. The results reveal that about 20% cells are killed with cold atmospheric plasma treatment. Doxorubicin as a regular anti-tumor drug shows 46% cell killing efficiency at the concentration of 4 μg/mL. After combined plasma treatment, the efficiency of cell killing is increased to 88% and the chemotherapy effect of doxorubicin is sensitized significantly. Moreover, cold atmospheric plasma combined gold nanorods presents 90% of cell killing efficiency, which is higher than gold nanorods alone (64%). In conclusion, cold atmospheric plasma can induce cell apoptosis and increase the uptake of chemotherapeutic drugs by changing cell membrane permeability, and sensitize the chemotherapy effect.

Abstract:In this study, the application of nonthermal plasma technology in the inactivation of ribonuclease was discussed, and the influence of acting gas and plasma generator on the inactivation performance was analyzed. The experimental results show that ribonuclease can be inactivated effectively by nonthermal plasma. Moreover, the inactivation performance will be obviously improved by mixing oxygen or water into the acting gas. Also, compared with surface dielectric barrier discharge plasma, the inactivation performance of ribonuclease is better by using floating-electrode dielectric barrier discharge generator.

Abstract:In this work, a floating-electrode dielectric barrier discharge plasma device was constructed based on the principle of dielectric barrier discharge, and its application of bacterial inactivation was studied. The experimental results show that the device has a significant sterilization performance in the inactivation of Staphylococcus aureus and Escherichia coli. The inactivation efficiency of Staphylococcus aureus and Escherichia coli is more than 99.99% within 30 s. Treatment gap distance also plays an important role in sterilization and the best distance is 1 mm.

Abstract:The research focuses on the effect of cold plasma treatment on polylactic acid film with different time (0, 15 s, 30 s, 45 s and 60 s), to determine the film morphology and hydrophilicity. Based on that, the polylactic acid films treated with cold plasma were immersed in nisin solution, and the antimicrobial activity was evaluated. The results indicate that cold plasma time can significantly change the hydrophilicity and roughness of the film surface. Moreover, it is found that with the cold plasma time increases, the roughness firstly increases and then decreases, whereas, the water angle initially decreases and then increases. Furthermore, the polylactic acid films with 60 s cold plasma treatment present a better antimicrobial ability against Listeria monocytogenes. Herein, it is concluded that cold plasma treatment can improve the applicability of polylactic acid film in antimicrobial food packaging.

Abstract:Polysaccharides have attracted wide attention due to their renewable, biocompatibility and low cost. The objective of this research was to study the effect of cold plasma treatment on the properties of sodium carboxymethyl cellulose and sodium alginate. The viscosity, pH, total viable colonies and 1,1-diphenyl-2- picrylhydrazyl values were determined. Besides, the structures and mechanisms of sodium carboxymethyl cellulose and sodium alginate were also discussed. Results indicate that sodium carboxymethyl cellulose and sodium alginate modified with cold plasma treatment obtained antimicrobial and antioxidant ability. This is mainly attributes to the energy produced during plasma treatment breaks the molecular bonds within polysaccharides, meanwhile some active groups containing oxygen and nitrogen are introduced. Then the active groups could combine with the broken molecular band, lead to some functional properties. Compared with some traditional methods such as acid and alkali exaction, cold plasma treatment possesses stability and high efficiency, without any chemical pollution. Thus, cold plasma treatment provides a new method for the preparation of functional polysaccharides.