Papers by Author: Ling Li Zhang

Abstract: Vibration and radiated sound of Air Conditioning are harmful to environment and safeness. Air Conditioning Compressor is its major part bringing vibration. To lower noise of a compressor and to improve its sound characteristic, the paper probes into a method indirect measurement of vibration, which both vibration and radiation behavior is represented using acoustic signal and theory of radiation modes. The paper investigates on the basic coupling relationship between structural vibration and acoustic radiation by means of the real modal analysis theory. Besides, the vibration and acoustic radiation characteristics of the rotary compressor are identified through the experiment method. According to the experimental results, between the vibration modes and the acoustic radiation modes have the comparability about the parameters. Therefore, this paper put forward a new method to the Active Structural Acoustic Control (ASAC), and provides the theoretical foundation of indirect measurement of vibration by using acoustic signal.

Abstract: Calcium phosphate (Ca-P) biomaterials have been proved to show osteoinductivity, however the affecting factors and mechanism are still unclear now. In this study, the surface characteristics of biphasic Ca-P ceramics (hydroxyapatite/tricalcium phosphate; HA/TCP) sintered at the distinct temperature were investigated and the mechanism of the osteoinductivity was discussed. The osteoinductivity of HA/TCP ceramics increased with decreasing the sintering temperature. The different surface micro-structure resulted from different sintering temperature includes phase composition, surface micro-structure, and surface potential. These characteristics should be the important factors affecting osteoinductivity.

Abstract: The objective of this study was to develop an efficient method for the production of bioactive bone morphogenetic protein 2 (BMP-2). A recombinant plasmid encoding mature human BMP-2 was transferred and expressed at a high level in E.coli. Most of the aimed proteins existed in inclusion bodies. The non-active recombinant human BMP-2 (rhBMP-2) monomer in inclusion bodies was refolded and simultaneously purified using hydroxyapatite (HA) chromatography. After oxidization of the monomer, the rhBMP-2 dimmer showed biological activity by the induction of alkaline phosphate activity in C2C12 cells. The refolding yield was about 30% and the purity was about 90% just by one chromatography process.

Abstract: The osteoinduction of Calcium Phosphate (CaP) had been proved and generally been investigated by in vivo implantation. However, the mechanism of the osteoinductivity was not clear and it was difficult to judge the osteoinductivity in vitro. In this study, Mouse C2C12 cell line, a kind of myoblast precursor cell, was employed to co-culture with CaP. The induction of cell differentiation by materials was tested by MTT method, fluorescence observation, especially the mRNA expression of Osteocalcin, Type I collagen and Fibronectin by RT-PCR. It was founded that C2C12 cells could be induced to expression osteocalcin when growth on the surface of the HA/TCP ceramics. At the same time, the ceramics with different composition and sintering temperature seemed to induce difference expression level of the related genes. The results proved that phase composition was one of the most important factors in the regulation of bone-related genes. This study provided a potential model to evaluate the osteoinductivity of CaP ceramics in vitro.

Abstract: A nano-grade hydroxyapatite/collagen composite was prepared by an in situ synthesis technique from calcium nitrate, diammoniun hydrogen phosphate, and a cowhide collagen sol at low temperature. XRD and TEM analyses of the composite indicated that crystals formed in the collagen fibril matrix were nanohydroxyapatite with low crystallinity. Biocompatibility of the composite was evaluated by in vitro cytotoxicity test and in vivo genotoxicity and sensitization test. No mutagenic activity of the composite was observed in mouse micronucleus tests. No evidence of dermal sensitization of the composite was found in guinea pig maximization tests. The results from a filter diffusion test indicated that the composite did not induce a cytotoxic behavior. All these results suggest that the composite has excellent biocompatibility.