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The biological HA in the body differs from that of pure HA in stoichiometry, composition, physical properties and mechanical properties, because this HA is particularly prone to ion substitution. As a cation that can substitute for calcium in the structure of hydroxyapatite, strontium provokes an increasing interest because of its beneficial effect on bone formation, and prevention of bone resorption. Here, strontium-substituted HA powders were prepared by the hydrothermal method at 180℃ for 8 h using Ca(NO3)2·4H2O, (NH4)2HPO4 and Sr(NO3)2 as reagents. X-ray diffraction, Fourier transform infrared spectroscope, transmission electron microscope, energy dis- persive X-ray, and thermogravimetric-differential thermal analysis were employed to investigate the crystalline phase, chemical composition, morphology, and thermal stability of the Sr-HA. And the cytotoxicity of Sr-HA was analyzed through MTT assay. The results show that Sr is incorporated into the HA crystal structure and the crystal grain size of the Sr-HA decreases as the Sr content (under 50wt%) is increased. Moreover, the HA thermal stability decreases. However, there's no apparent difference between the pure hydroxyapatite and all of the Sr-HA groups in cytotoxicity, which may have good biocompatibility.

Background When studying and designing an artificial bone in vitro with similar features and functionality of natural bone by tissue engineering technology, the culturing environment, especially the mechanical environment is supposed to be an important factor, because a suitable mechanical environment in vitro may improve the adaptability of the planted-in tissue engineering bone in the body. Unfortunately, up to now, the relationship between mechanical stimuli and natural bone growth has not yet been precisely determined, and it is so imperative for a prior study on effect of mechanical loading on growth of the natural bone cultured in vitro. Methods Under sterile conditions, explant models of rabbit cancellous bone with 3 mm in thickness and 8 mm in diameter were prepared and cultured in a dynamic loading and circulating perfusion bioreactor system. By Micro-CT scanning, a 3D model for finite element (FEM) analysis was achieved. According to the results of FEM analysis and physiological load bearing capacity of the natural bone, these models were firstly subjected to mechanical load with 1Hz frequency causing average apparent strain of 1000 μϵ, 2000 μϵ, 3000 μϵ and 4000 μϵ respectively for 30 min every day, activities of alkaline phosphatase (AKP) were detected on the 5th and the 14th loading day and on the 14th and the 21st day, mechanical properties, tissue mineral density (TMD) of the bone explant models were investigated and Von-kossa staining and fluorescence double labeling assays were conducted to evaluate whether there were fresh osteoid in the bone explant models. In addition, Western blot, Elisa and Real-time PCR were employed to analyze expression of Collagen-I (COL-1), bone morphogenetic protein-2 (BMP-2) and osteoprotegerin (OPG) protein and RNA. Results The explant models of rabbit cancellous bone prepared under sterile conditions grew well in the bioreactor system. With the increasing culturing time and load levels, bone explant models in groups with 1000 μϵ and 2000 μϵ average apparent strain experienced improving mechanical properties and TMD (P Conclusion Our study demonstrated that mechanical load could improve function and activity of osteoblasts in explant models of cancellous bone. Through regulations of COL-1, OPG and BMP-2 secreted by osteoblasts, the mechanical load could improve the tissue structural density and stiffness due to formation of fresh osteoid.

The aim of this study was to investigate the threedimensional microstructure of bovine cancellous bone as an ideal scaffold for bone tissue engineering using a highresolution micro-Computed Tomography (micro-CT) system. The xenogeneic cancellous bone harvested from bovine ilium was scanned by the micro-CT after a set of physicochemical treatment. The structural parameters obtained from micro-CT were analyzed to evaluate biomechanical properties of the xenogeneic cancellous bone used as the scaffold in bone tissue engineering. The bone volume fraction (BV/TV), degree of anisotropy(DA), Euler Number, trabecular thickness (Tb.Th), and the three radii of the mean intercept length (MIL) ellipsoid (a1,a2, and a3) were recorded. A non-invasive visualization and measurement was explored effectively by combining micro-CT as a novel imaging technology with Finite Element (FE) method.Surface meshes generated in medical image processing software MIMICS based on micro-CT images were converted into finite element models which were assigned material properties according to the Gray Value. All the FE models of samples were ultimately subjected to physiological apparent strain using FE analysis software to figure out the local strain. This approach also shed light on the correlation between strain and stress about the specific scaffold material. The results showed that the four microstructural parameters in both strain groups were in normal distribution and homogeneity of variance, except for Euler Number, and no statistically significant change in both different load groups could be detected. Moreover, for an accurate prediction of the mechanical properties of the xenogeneic cancellous bone, it was more reasonable that bone mineral density was made correlate with the Gray Value of segmented 3D images, which were better than those studies based on the isotropy hypothesis.

Due to the mutual interference and sharing of wireless links in TDMA ad hoc networks, conflicts will occur when data message are transmitting between nodes. The broadcast scheduling problem (BSP) is aim to schedule each node in different slot of fixed length frame at least once, and the objective of BSP is to seek for the optimal feasible solution, which has the shortest length of frame slots as well as the maximum node transmission. In this paper, we propose a two stage hybrid algorithm based on fuzzy Hopfield neural network to solve this BSP in ad hoc. In the first stage, we use a modified sequential vertex coloring algorithm to obtain a minimal TDMA frame length. Experimental results, obtained from the running on three benchmark graph, show that our algorithm can achieve better performance with shorter frame length and higher channel utilizing ratio than other exit BSP solutions.

Due to the convenience of Internet, people can search for whatever information they need and buy whatever they want on the web. In the age of E-Commerce, it is important for firms to develop web-based marketing strategy such as product bundling to increase revenue. Recommendation system(RS) is a platform that can be used to reduce the searching cost of consumers, increase the effectiveness of firm's promotion strategies and enhance consumer's loyalty. This paper propose a web-based collaborative filtering mechanism for firm's product bundling strategy. First, Clustering using Adaptive Resonance Theory is applied to generate different kinds of customer group, in which members have same attributes or habits. Second, Data Mining using association rule techniques is applied to find the relations between two products in given support and confidence values. And last, the RS value is calculated to generate personal product bundling list and top-N recommendations. Experiment results also show that it is a feasible and effective design scheme.