Search

In recent years, the development of ultrasound contrast agents has encouraged their use as a drug system for diagnosis and therapy. In this paper, polylactic acid (PLA) composite microbubbles (FA/DOX/GO/DOX/PLA) were prepared with graphene oxide (GO) as a carrier of the targeted factor folic acid (FA) and doxorubicin (DOX) by the multiple emulsification–solvent evaporating process. Appearance, particle size, and zeta potential of PLA composite microbubbles were characterized by using a nanoparticle size analyzer and transmission electron microscopy. Breast cancer cells MCF-7 were used to evaluate the antitumor activity of PLA composite microbubbles in vitro by using the CCK-8 and acridine orange staining method. The ultrasonic imaging effect of PLA composite microbubbles was investigated in New Zealand white rabbits by the Doppler color ultrasound imaging system. With Kunming mice as the research model, the acute toxicity of PLA composite microbubbles was examined. The experimental results showed that the prepared PLA composite microbubbles presented a hollow and spherical shape with a particle size of 600 nm or so and a zeta potential of −37.5 ± 10.0 mV. They had a good effect of the enhancing imaging, and clear ultrasound imaging can be obtained. PLA composite microbubbles showed a significant proliferation inhibition effect on breast cancer cells MCF-7 in a dose-dependent manner. After PLA composite microbubbles were modified by FA, they were good for targeting FA receptors on the surface of MCF-7 cells, which increased the inhibition rate of the tumor cells. LD50 of PLA composite microbubbles was 87.529 mg·kg–1; the mice did not show the acute toxicity when the dose of composite microbubbles was lower than this value.

With Span and polyethylene glycol (PEG) as the membrane material, the as-prepared folate–carbon nanotube–paclitaxel (FA–CNT–PTX) complex was added to the reaction system under sound vibration cavitation and Span–PEG with FA–CNT–PTX microbubbles was obtained. The maximum tolerating dose of the obtained composite microbubbles on Kunming mice was determined by acute toxicity test. Utilizing the breast cancer tumor model in the nude mice to assess the anti-tumor activity in vivo, the inhibition effect of the composite microbubbles on tumor growth was analyzed by recording the weight and tumor volume of the nude mice. HE staining observations, the immunohistochemistry method, and TUNEL were, respectively, used to examine the inhibition effect of the composite microbubbles on breast cancer tumors in the nude mice. The ultrasound imaging effects and the changes in the peak intensities of the composite microbubbles were inspected using a Doppler color ultrasound imaging system. The experimental results showed that the maximum tolerated dose of the composite microbubbles was 3500 mg kg−1, indicating that the composite microbubbles had low toxicity and good biocompatibility. The composite microbubbles could reach the breast cancer tumor via a targeting factor, and then hindered the tumor growth by inhibiting the proliferation of tumor cells and inducing apoptosis of the tumor cells. The composite microbubbles contributed toward enhancing the ultrasound signal and improved the resolution of the ultrasound images and extended the imaging time. Also, the addition of CNTs in the composite microbubbles could enhance the ultrasound contrast. Simultaneously, the peak intensity at the tumor was significantly reduced after the treatment.

In this paper, the Apriori association rules mining algorithm is studied in-depth, and the algorithm is realized by MATLAB. To further avoid blind search in the process of mining and improve the efficiency of frequent itemset search, the improved technology of the Apriori algorithm is studied, and the application of the improved Apriori algorithm in teaching management is studied. The proportion of application and research data mining in the teaching management system of colleges and universities is still low, especially in the management of students’ scores, because there are many students, the amount of students’ scores that need to be counted is large.

A sub-circuit model is proposed for the power VDMOS device by using the parasitic resistors RS/RD/RG/RDS and the parasitic diode D based on the MOSFET model in this paper. It should be noted that RD is not a fixed resistance, but a variable resistance controlled by the gate voltage and the drain voltage to improve the accuracy of the spice model. This model is well verified by the TCAD simulation data.

In this paper, a novel structure is proposed to improve SEB performance of 650V SJVDMOS. The hardened structure integrates a graded doping buffer layer and a P type buried layer. 2D Synopsys sentaurus TCAD simulation is used to evaluate the SEB performance of the device. The simulation results show that the safe operating area (SOA) of the new device is greatly increased under the heavy ions incidence. The SEB threshold voltage of the device improves from 105V to 695V, successfully achieves SEB immunity. At the same time, the hardened structure also maintains good steady-state characteristics

In this paper, a new base resistance controlled thyristor with N-type buried layer (NBL-BRT) is proposed. The N-type buried layer introduces an electron potential trap to extract electron current from the n-channel MOSFET to thyristor region, which improves the effective trigger current, and then suppresses the snapback phenomenon during forward conduction state. Meanwhile, NBL-BRT maintains high blocking capability by controlling the doping level (N BL ) of the N-type buried layer. Compared with conventional BRT, the proposed BRT structure with doping level of N-type buried layer of 1.0 × 1015 cm-3 reduces the ΔV SB by 64.21%.