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In recent years, light-emitting diodes (LEDs) technology, known as “Green Illumination”, is growing rapidly. LED communications, or visible light communications is a promising field and is getting more and more research focus. LED is the major source of nonlinearity in LED communications, and the nonlinearity needs to be modelled effectively and thereby mitigated through pre-distortion or post-distortion to avoid severe degradation of communication performance.

The light-emitting diode (LED) is the major source of nonlinearity in LED communications, and the nonlinearity needs to be effectively modelled and mitigated to avoid the degradation of communication performance. In indoor LED communications, multipath dispersion can lead to inter-symbol interference (ISI) at high data rates. In this paper, we jointly estimate the LED nonlinearity and ISI channel based on an orthogonal polynomial based technique. Then frequency domain equalization and post-distortion are adopted to mitigate the ISI and nonlinearity. Simulation results are provided to demonstrate the effectiveness of the proposed technique.

The light-emitting diode (LED) is the major source of nonlinearity in LED communication systems, which needs to be carefully handled to avoid significant performance degradation. Post-distortion is an effective and convenient way to compensate the nonlinear distortion at the receiver side. In this work, we propose a soft-in-soft-out (SISO) post-distorter, which works with a SISO decoder iteratively by exchanging log-likelihood ratios (LLRs) of the coded bits at the receiver. It is demonstrated that the proposed iterative technique can achieve a remarkable performance gain compared to the conventional post-distortion technique in the literature.

Shiyang Zhang,1 Qiming Yang,1 Weikang Zhao,1 Bo Qiao,1 Hongwang Cui,1 Jianjun Fan,2 Hong Li,3 Xiaolin Tu,4 Dianming Jiang1 1Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, 2Molecular Medicine and Cancer Research Centre, Chongqing Medical University, Chongqing, 3College of Physical Science and Technology, Sichuan University, Chengdu, 4Institutes of Life Sciences, Chongqing Medical University, Chongqing, People’s Republic of China Abstract: Graphene and its derivatives have been receiving increasing attention regarding their application in bone tissue engineering because of their excellent characteristics, such as a vast specific surface area and excellent mechanical properties. In this study, graphene-reinforced nanohydroxyapatite/polyamide66 (nHA/PA66) bone screws were prepared. The results of scanning electron microscopy observation and X-ray diffraction data showed that both graphene and nHA had good dispersion in the PA66 matrix. In addition, the tensile strength and elastic modulus of the composites were significantly improved by 49.14% and 21.2%, respectively. The murine bone marrow mesenchymal stem cell line C3H10T1/2 exhibited better adhesion and proliferation in graphene reinforced nHA/PA66 composite material compared to the nHA/PA66 composites. The cells developed more pseudopods, with greater cell density and a more distinguishable cytoskeletal structure. These results were confirmed by fluorescent staining and cell viability assays. After C3H10T1/2 cells were cultured in osteogenic differentiation medium for 7 and 14 days, the bone differentiation-related gene expression, alkaline phosphatase, and osteocalcin were significantly increased in the cells cocultured with graphene reinforced nHA/PA66. This result demonstrated the bone-inducing characteristics of this composite material, a finding that was further supported by alizarin red staining results. In addition, graphene reinforced nHA/PA66 bone screws

Ao Zhou,1 Shuo Chen,1,2 Bin He,1 Weikang Zhao,1 Xiaojun Chen,1 Dianming Jiang1 1Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 2Department of Orthopedics, Dujiangyan Medical Center, Dujiangyan, People’s Republic of China Abstract: Bioactive mediators, cytokines, and chemokines have an important role in regulating and optimizing the synergistic action of materials, cells, and cellular microenvironments for tissue engineering. RADA self-assembling peptide hydrogels have been proved to have an excellent ability to promote cell proliferation, wound healing, tissue repair, and drug delivery. Here, we report that D-RADA16 and L-RADA16-RGD self-assembling peptides can form stable second structure and hydrogel scaffolds, affording the slow release of growth factor (transforming growth factor cytokine-beta 1 [TGF-beta 1]). In vitro tests demonstrated that the plateau release amount can be obtained till 72 hours. Moreover, L-RADA16, D-RADA16, and L-RADA16-RGD self-assembling peptide hydrogels containing TGF-beta 1 were used for 3D cell culture of bone mesenchymal stem cells of rats for 2 weeks. The results revealed that these three RADA16 peptide hydrogels had a significantly favorable influence on proliferation of bone mesenchymal stem cells and hold some promise in slow and sustained release of growth factor. Keywords: molecular self-assembly, self-assembling peptide, hydrogel scaffolds, controlled release, TGF-beta 1, bone mesenchymal stem cells

The light-emitting diode (LED) is the major source of nonlinearity in LED communications, and the nonlinearity needs to be effectively modeled and thereby mitigated through predistortion or postdistortion to avoid degradation of communication performance. A memory polynomial is often used for LED nonlinearity modeling and mitigation in the literature. However, the estimation of memory polynomial coefficients suffers from numerical instability, resulting in inaccurate modeling and poor performance in nonlinearity mitigation. In this paper, we propose an orthogonal polynomial-based nonlinearity modeling and mitigation technique for LED communications with pulse amplitude modulation (PAM) signaling and show that the proposed technique significantly outperforms the conventional memory polynomial-based techniques.

Bin He,1 Yunsheng Ou,1 Ao Zhou,1 Shuo Chen,1 Weikang Zhao,1 Jinqiu Zhao,2 Hong Li,3 Yong Zhu,1 Zenghui Zhao,1 Dianming Jiang1 1Department of Orthopedics, 2Department of Infectious Diseases, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 3School of Physical Science and Technology, Sichuan University, Chengdu, People’s Republic of China Abstract: Bone defects are very common in orthopedics, and there is great need to develop suitable bone grafts for transplantation in vivo. However, current bone grafts still encounter some limitations, including limited availability, immune rejection, poor osteoinduction and osteoconduction, poor biocompatibility and degradation properties, etc. Self-assembling peptide nanofiber scaffolds have emerged as an important substrate for cell culture and bone regeneration. We report on the structural features (eg, Congo red staining, circular dichroism spectroscopy, transmission electron microscopy, and rheometry assays) and osteogenic ability of D-RADA16-RGD peptide hydrogels (with or without basic fibroblast growth factor) due to the better stability of peptide bonds formed by these peptides compared with those formed by L-form peptides, and use them to fill the femoral condyle defect of Sprague Dawley rat model. The bone morphology change, two-dimensional reconstructions using microcomputed tomography, quantification of the microcomputed tomography analyses as well as histological analyses have demonstrated that RGD-modified D-form peptide scaffolds are able to enhance extensive bone regeneration. Keywords: bone defect, functionalized D-form self-assembling peptide, D-RADA16-RGD, peptide hydrogel, bone regeneration