A Low-Complexity Signal Detection Utilizing AOR Iterative Method for Massive MIMO Systems

Massive multiple-input multiple-output(MIMO) system is capable of substantially improving the spectral efficiency as well as the capacity of wireless networks relying on equipping a large number of antenna elements at the base stations. However, the excessively high computational complexity of the signal detection in massive MIMO systems imposes a significant challenge for practical hardware implementations. In this paper, we propose a novel minimum mean square error(MMSE) signal detection using the accelerated overrelaxation(AOR) iterative method without complicated matrix inversion, which is capable of reducing the overall complexity of the classical MMSE algorithm by an order of magnitude. Simulation results show that the proposed AOR-based method can approach the conventional MMSE signal detection with significant complexity reduction.

Fine-tuning Bacterial Cyclic di-AMP Production for Durable Antitumor Effects Through the Activation of the STING Pathway

The stimulator of interferon genes(STING)protein is an important and promising innate immune target for tumor therapy.However,the instability of the agonists of STING and their tendency to cause systemic immune activation is a hurdle.The STING activator,cyclic di-adenosine monophosphate(CDA),produced by the modified Escherichia coli Nissle 1917,shows high antitumor activity and effectively reduces the systemic effects of the“off-target”caused by the activation of the STING pathway.In this study,we used synthetic biological approaches to optimize the translation levels of the diadenylate cyclase that catalyzes CDA synthesis in vitro.We developed 2 engineered strains,CIBT4523 and CIBT4712,for producing high levels of CDA while keeping their concentrations within a range that did not compromise the growth.Although CIBT4712 exhibited stronger induction of the STING pathway corresponding to in vitro CDA levels,it had lower antitumor activity than CIBT4523 in an allograft tumor model,which might be related to the stability of the surviving bacteria in the tumor tissue.CIBT4523 exhibited complete tumor regression,prolonged survival of mice,and rejection of rechallenged tumors,thus,offering new possibilities for more effective tumor therapy.We showed that the appropriate production of CDA in engineered bacterial strains is essential for balancing antitumor efficacy and self-toxicity.

Creep-fatigue crack growth behavior in GH4169 superalloy

This study aims to examine the crack growth behavior of turbine disc GH4169 superalloy under creepfatigue loading. Crack growth experiments were performed on compact tension specimens using trapezoidal waveform with dwell time at the maximum load at 650℃. The crack growth rate of GH4169 superalloy significantly increased with dwell time. The grain boundaries oxidize during the dwell process, thereby inducing an intergranular creep-fhtigue fracture mode. In addition, testing data under the same dwell time showed scattering at the crack growth rate. Consequently, a modified model based on the Saxena equation was proposed by introducing a distribution factor for the crack growth rate. Microstructural observation confirmed that the small grain size and high volume fraction of the δ phase led to a fast creep-fatigue crack growth rate at 650℃, thus indicating that two factors, namely, fine grain and presence of the δ phase at the grain boundary, increased the amount of weakened interface at high temperature, in which intergranular cracks may form and propagate.

Progress in the research and development of nerve conduits

The reconstruction after peripheral nerve damage, especially for long‐segment nerve defects, remains a clinical challenge. Autologous nerve graft transplantation is an efficient method for the repair of peripheral nerve defects, but the involved com‐plications and shortcomings have greatly limited the clinical efficacy of treatments offered to patients with nerve defects. Thus, there is an urgent need to develop new therapeutic strategies and explore alternatives to autologous nerve transplantation in clinical practice, based on the knowledge of the peripheral nerve regeneration mechanism and biological histocompatibility principles. With significant advances in the research and application of nerve conduits, they have been used to repair peripheral nerve injury for several decades. In this paper, the study background of nerve conduits, their applications in clinic, status of conduit material research and construction of tissue‐engineered artificial nerves were reviewed.

Controlled release of nerve growth factor and basic fibroblast growth factor combined with small-gap anastomosis enhances sciatic nerve regeneration

Objectives: Nerve regeneration after peripheral nerve injury is a slow process with a limited degree of functional recovery, resulting ina high disability rate. Thus, accelerating the rate of nerve regeneration and improving the degree of nerve repair is a clinical challenge. This study aimed to investigate the role of growth factor gel combined with small‐gap nerve anastomosis in the regeneration of sciatic nerve injury in rats. This was achieved by injecting nerve growth factor(NGF) and basic fibroblast growth factor(bF GF) gel into a silicon chamber that bridged the transection of the nerve. Methods: In 27 randomly chosen Sprague Dawley rats, a sharp blade was used to transect the right hind leg sciatic nerve. The rats were divided into 3 groups: in groups A and B, silicon tubes containing NGF and bF GF gel or saline, respectively, were used to bridge the nerve proximal and distal ends(3‐mm gap), and in group C, the nerve proximal and distal ends were directly sutured. Eight weeks after surgery, the sciatic nerve function index, neural electrophysiology, and muscle wet weight as well as histological, ultrastructural, and immunohistochemical parameters were evaluated.Results: The sciatic nerve function index, nerve conduction velocity, muscle wet weight,density of regenerated nerve fibers, and myelination in group A were better than those in group Bor C, but the sciatic nerve function index, muscle wet weight, and thickness of myelination in the 3 groups were not significantly different3(P > 0.05). There were no significant differences innerve conduction velocitybetween groups A and B(P > 0.05),but it was higher in both groups than that of group C(P < 0.05). The regenerated nerve fiber densityin the 3 groups showed significant differences(P < 0.05). Conclusions: Small‐gap nerve anastomosis can provide a good regenerative microenvironment for rat sciatic nerve regeneration, and the combined strategy of growth factor gel with small‐gap nerve anastomosis appears to havea superior effect on nerve repair.