| 1 | A digital open-loop Doppler processing prototype for deep-space navigation显示文摘A prototype based on digital radio technology with associated open-loop Doppler signal processing techniques has been developed to measure a spacecraft's line-of-sight velocity. The prototype was tested in China's Chang'E-1 lunar mission relying on S-band telemetry signals transmitted by the sat-ellite,with results showing that the residuals had a RMS value of ~3 mm/s (1σ ) using 1-sec integration,which is consistent with the Chinese conventional USB (Unified S-Band) tracking system. Such preci-sion is mainly limited by the short-term stability of the atomic (e.g. rubidium) clock at the uplink ground station. It can also be improved with proper calibration to remove some effects of the transmission media (such as solar plasma,troposphere and ionosphere),and a longer integration time (e.g. down to 0.56 mm/s at 34 seconds) allowed by the spacecraft dynamics. The tracking accuracy can also be in-creased with differential methods that may effectively remove most of the long-term drifts and some of the short-term uncertainties of the uplink atomic clock,thereby further reducing the residuals to the 1 mm/s level. Our experimental tracking data have been used in orbit determination for Chang'E-1,while other applications (such as the upcoming YH-1 Mars orbiter) based on open-loop Doppler tracking will be initiated in the future. Successful application of the prototype to the Chang'E-1 mission in 2008 is believed to have great significance for China's future deep space exploration. | JIAN NianChuan SHANG Kun ZHANG SuJun WANG MingYuan SHI Xian PING JingSong YAN JianGuo TANG GeShi LIU JunZe QIU Shi FUNG Lai-Wo ZHANG Hua WANG Zhen GOU Wei | 2009 | Science China(Physics,Mechanics & Astronomy)2009，52，12： | 2 |
| 2 | Mesenchymal stem cell exosomes inhibit nucleus pulposus cell apoptosis via the miR-125b-5p/TRAF6/NF-κB pathway axis显示文摘Intervertebral disc degeneration(IVDD)is the pathological basis of a range of degenerative spinal diseases and is the primary cause of lower back pain.Mesenchymal stem cell(MSC)transplantation inhibits IVDD progression.However,the specific mechanisms that underlie these effects remain unclear.In this study,candidate microRNAs(miRNAs)are screened using bioinformatics and high-throughput sequencing.TNF-αis used to induce nucleus pulposus cell(NPC)degeneration.MSC-derived exosomes(MSC-exosomes)are obtained using high-speed centrifugation and identified by transmission electron microscopy(TEM),nanoparticle tracking analysis(NTA)and western blot analysis.Cell viability is determined by CCK-8 assay.Flow cytometry and TUNEL assays are used to detect cell apoptosis.The expression levels of miR-125b-5p are detected by RT-qPCR,and a dual-luciferase gene reporter assay confirms the downstream target genes of miR-125b-5p.Protein expression is determined by western blot analysis.Rat models are used to validate the function of miR-125b-5p in MSC-exosomes.The results show that miR-125b-5p is expressed at low levels in degenerated disc tissues compared with that in normal disc tissues;however,it is highly expressed in MSC-exosomes.Furthermore,MSC-exosomes are efficiently taken up by NPCs while miR-125b-5p is delivered into NPCs;thus,MSC-exosomes act as inhibitors of apoptosis in NPCs.Overexpression of miR-125b-5p downregulates TRAF6 expression and inhibits NF-κB activation.However,TRAF6 overexpression reverses these effects of miR-125b-5p.We demonstrate that MSC-exosomes attenuate IVDD in vivo by delivering miR-125b-5p.MSC-exosomes can deliver miR-125b-5p to target TRAF6,inhibit NF-κB activation,and attenuate the progression of IVDD. | Yang Duan Cheng Yu Wenhao Kuang Jianjun Li Sujun Qiu Songjia Ni Zhong Chen | 2023 | Acta Biochimica et Biophysica Sinica2023，55，12： | 0 |
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