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Electrical stimulation (ES) plays an important role in regulating cell osteoblast differentiation. As a noninvasive rehabilitation therapy method, Es has a unique role in postoperative recovery. Bone morphogenetic protein-2 (BMP-2) is the most commonly used bioactive molecule in in situ tissue engineering scaffolds, and it plays an important regulatory role in the whole process of bone injury repair. In this study, the osteogenic regulation of MC-3T3-E1 cells was studied by combining pulsed electrical stimulation (PES) and different concentrations of BMP-2. The results showed that PES and BMP-2 could synergically promote the proliferation of MC-3T3-E1 cells. The qPCR results of osteoblast-related genes showed that PES was synergistic with BMP-2 to promote osteoblast differentiation mainly through the regulation of the Smad/BMP and insulin like growth factor 1 (IGF1) signaling pathways. The expression level of alkaline phosphatase (ALP) and alizarin red staining further demonstrated the synergistic effect of PES and BMP-2 on promoting osteogenic differentiation and mineralization of cells. PES and BMP-2 could also synergically promote cell proliferation, expression of collagen I (COL-I) and ALP, and cell mineralization on the 3D-printed polylactic acid scaffold. These results suggest that the use of PES can enhance the osteogenic effect of in situ bone repair scaffolds containing BMP-2, reduce the dose of BMP-2 alone, and reduce the possible side effects of high-dose BMP-2 in vivo. [ABSTRACT FROM AUTHOR]

This paper investigates the Resource allocation problem in OFDMA-based decode-and-forward cooperative communication systems. The objective is to maximize the sum throughput under the constraints of joint total transmission power and subchannels occupation, while maintaining the maximum fairness among multiple relay nodes. Since the optimal solution to this combinatorial problem is extremely computationally complex to obtain, we propose a low-complexity suboptimal algorithm that allocates subchannel and power separately. In the proposed algorithm, subchannel allocation over the relay nodes is first performed under the assumption of equal power distribution. Then, an optimal power allocation algorithm named multi-level water-filling is used to maximize the sum rate. The simulation results show that the performance of the proposed algorithm can approach asymptotically to that of the optimal algorithm while enhancing the fairness among all relay nodes and reducing computational complexity from exponential to linear with the number of subchannels. It is also shown that the proposed equal power distribution algorithm with subchannel permutation (SP) outperforms the one without SP. [ABSTRACT FROM AUTHOR]

An iterative receiver is proposed based on the EM (Expectation-Maximization) algorithm for an OFDM-SDMA (Orthogonal Frequency Division Multiplexing-Space Division Multiple Access) system. By using a few pilots in every OFDM symbol, both channel estimation and multiuser detection can be simultaneously obtained by iteration. The computer simulation results show this receiver can track channel variations and detect multiuser symbols for different number of users under time-varying multipath channels. [ABSTRACT FROM AUTHOR]