Zhensheng Li

This study investigated the use of three-dimensional porous chitosan-alginate (CA) scaffolds for critical size calvarial defect (diameter, 5.0 mm) repair in Sprague-Dawley rats. CA scaffolds have been used for in vitro culture of many cell types and demonstrated osteogenesis in ectopic locations in vivo, but have yet to be evaluated for functional bone tissue engineering applications. CA scaffolds demonstrated the ability to support undifferentiated mesenchymal stem cells (MSCs) in culture for 14 days in vitro and promoted spherical morphology. In vivo tests were performed using CA scaffolds and CA scaffolds with treatments including undifferentiated MSCs, bone marrow aspirate, and bone morphogenetic protein-2 (BMP-2) growth factor in comparison to unfilled bone defect used as a control. The samples were analyzed with MicroCT, histology, and immunohistochemical staining at 4 and 16 weeks. Partial defect closure was observed in all experimental groups at 16 weeks, with the greatest defect closure (71.56 ± 19.74%) in the animal group treated with CA scaffolds with BMP-2 (CA + BMP-2). The experimental samples demonstrated osteogenesis in histology and immunohistochemical staining, with the CA + BMP-2 group, showing the greatest level of osteogenesis. Tissue engineered CA scaffolds show promise in reconstruction of critical size bone defects.

The special nonlinear effect of sinking bubbles is observed when the container partially filled with a liquid is excited by vibration. This paper is concerned with this interesting phenomenon in an incompressible viscous fluid under vertical vibration. We construct the theoretical model from the view of vibration mechanics and fluid mechanics. According to theoretical analysis, we derive the accurate model of the bubble moving in the liquid and the added mass caused by it. After that, the control equation of the bubble is given by the force analysis and the differential equation of variable-mass systems. Besides, the critical depth of the sinking bubble is derived based on the method of direct separation of motions. We further explore and analyze the specific reasons why the bubbles sink. At the same time, the conditions where the variable mass has a significant influence on the motion of the object are given. The main factors affecting the sinking of bubbles, density, frequency, and amplitude are numerically simulated and analyzed with different conditions. To prevent or weaken the effect of sinking bubbles in the oscillating fluid, feasible approaches are proposed. Meanwhile, the theory is validated experimentally.

Abstract Multi-walled carbon nanotubes (MWNTs) were used to adsorb low concentration erythromycin from natural water. The kinetic curves and adsorption isotherms were measured and the thermodynamic parameters were calculated. The effects of pH value, ionic strength and humic acid on the adsorption process were investigated. The results showed that the adsorption of carbon nanotubes to erythromycin was rapid in the first 40 min, and reached equilibrium within 200 min. The dynamics curve conforms to the quasi-second-order dynamics model. The Freundlich model can better fit the adsorption test data. Thermodynamic parameters show that the adsorption of Erythromycin by MWNTs is a spontaneous endothermic process. The adsorption activation energy Ea shows that the adsorption between MWNTs and erythromycin is a chemisorption process, and the content of oxygen-containing functional groups on the surface of CNTs determines the equilibrium adsorption amount. Ionic strength has obvious effect on adsorption. Increasing the pH value of the solution from 5 to 9 was beneficial to increasing the adsorption capacity of erythromycin. The adsorption capacity of carbon nanotubes to erythromycin was significantly increased with appropriate humic acid.