This paper studies the key techniques of the measurement and communication system for inter-satellite links(ISLs) of global navigation satellite system.A fixed link topology is designed based on the analysis of inter-...This paper studies the key techniques of the measurement and communication system for inter-satellite links(ISLs) of global navigation satellite system.A fixed link topology is designed based on the analysis of inter-satellite geometric properties and spatial parameters of the standard Walker24/3/2 constellation.This design can achieve full network coverage with small num-ber of hops,significantly reduce the number of ISLs,and enhance the feasibility and reliability of the system.A new time-division duplex mode,as well as an integrated measurement and communication scheme,is proposed based on the de-signed topology.Furthermore,mathematical formulas,error models,and modification methods regarding two-way ranging and time synchronization algorithms using spread spectrum non-coherent data frame for this new system are comprehensively dis-cussed.Theoretical analysis and simulation studies demonstrate that our design,compared with current GPS systems,has higher ranging and time synchronization precision,improved measurement efficiency,and higher channel utilization ratio and data transmission rate.It has no restrictions of constellation configuration,making it suitable for both MEO and the future MEO/GEO hybrid constellations.The results in this paper can serve as strong technical support for the next generation of GNSS ISL.展开更多
Objective Isoliquiritigenin （ISL）, a licorice chalconoid, is considered to be a bioactive agent with chemopreventive potential. This study investigates the mechanisms involved in ISL-induced apoptosis in human cervi...Objective Isoliquiritigenin （ISL）, a licorice chalconoid, is considered to be a bioactive agent with chemopreventive potential. This study investigates the mechanisms involved in ISL-induced apoptosis in human cervical carcinoma HeLa cells. Methods Cell viability was evaluated using a 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyl-tetrazolium bromide （MTT） assay. Apoptosis was determined by flow cytometry using an Annexin V-FITC Apoptosis Detection Kit. The intracetlular ROS levels were assessed using a 2, 7-dichlorofluorescein probe assay. The mitochondrial membrane potential was measured with the dual-emission potential-sensitive probe 5, 5＇, 6, 6＇-tetra-chloro-1, 1＇, 3, 3＇-tetraethyl-imidacarbocyanine iodide （JC-1）. The degradation of poly-ADP-ribose polymerase （PARP） protein, the phosphorylation of PKR-like ER kinase （PERK）, the phosphorylation of the a-subunit of eukaryotic initiation factor 2 （elF2a）, the expression of the 78 kD glucose-regulated protein （GRP 78）, and the activation of caspase-12 were analyzed via western blot analysis. Results ISL significantly inhibited the proliferation, the increase in ROS levels and apoptotic rates of HeLa cells in a concentration-dependent manner. Moreover, ISL induced mitochondrial dysfunction, caspase activation, and PARP cleavage, which displayed features of mitochondria dependent on apoptotic signals. Besides, exposure of HeLa cells to ISL triggered endoplasmic reticulum （ER） stress, as indicated by the increase in p-elF2a and GRP78 expression, ER stress-dependent apoptosis is caused by the activation of ER-specific caspase-12. Conclusion The findings from our study suggest that ISL-induced oxidative stress causes HeLa cel apoptosis via the mitochondrion-dependent and the ER stress-triggered signaling pathways.展开更多
The high-speed movement of satellites makes it not feasible to directly apply the mature routing scheme on the ground to the satellite network.DT-DVTR in the snapshot-based connectionoriented routing strategy is one o...The high-speed movement of satellites makes it not feasible to directly apply the mature routing scheme on the ground to the satellite network.DT-DVTR in the snapshot-based connectionoriented routing strategy is one of the representative solutions,but it still has room for improvement in terms of routing stability.In this paper,we propose an improved scheme for connection-oriented routing strategy named the Minimal Topology Change Routing based on Collaborative Rules(MTCR-CR).The MTCR-CR uses continuous time static topology snapshots based on satellite status to search for intersatellite link(ISL)construction solutions that meet the minimum number of topology changes to avoid route oscillations.The simulation results in Beidou-3 show that compared with DT-DVTR,MTCR-CR reduces the number of routing changes by about 92%,the number of path changes caused by routing changes is about38%,and the rerouting time is reduced by approximately 47%.At the same time,in order to show our algorithm more comprehensively,the same experimental index test was also carried out on the Globalstar satellite constellation.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60872062)the National Hi-Tech Research and Develop-ment Program of China ("863" Project) (Grant Nos.2007AA12Z336,2009AA12Z313)the Innovation Fund for Astronautics Key-Tech (Grant No. 2009-06)
文摘This paper studies the key techniques of the measurement and communication system for inter-satellite links(ISLs) of global navigation satellite system.A fixed link topology is designed based on the analysis of inter-satellite geometric properties and spatial parameters of the standard Walker24/3/2 constellation.This design can achieve full network coverage with small num-ber of hops,significantly reduce the number of ISLs,and enhance the feasibility and reliability of the system.A new time-division duplex mode,as well as an integrated measurement and communication scheme,is proposed based on the de-signed topology.Furthermore,mathematical formulas,error models,and modification methods regarding two-way ranging and time synchronization algorithms using spread spectrum non-coherent data frame for this new system are comprehensively dis-cussed.Theoretical analysis and simulation studies demonstrate that our design,compared with current GPS systems,has higher ranging and time synchronization precision,improved measurement efficiency,and higher channel utilization ratio and data transmission rate.It has no restrictions of constellation configuration,making it suitable for both MEO and the future MEO/GEO hybrid constellations.The results in this paper can serve as strong technical support for the next generation of GNSS ISL.
基金supported by the National Natural Science Foundation of China (No. 30960451)Major State Basic Research Development Program (2010CB535003)the Xinjiang production and construction corps funds for distinguished young scientists to ZHENG Qiu Sheng,international cooperation projects (2012BC001)
文摘Objective Isoliquiritigenin （ISL）, a licorice chalconoid, is considered to be a bioactive agent with chemopreventive potential. This study investigates the mechanisms involved in ISL-induced apoptosis in human cervical carcinoma HeLa cells. Methods Cell viability was evaluated using a 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyl-tetrazolium bromide （MTT） assay. Apoptosis was determined by flow cytometry using an Annexin V-FITC Apoptosis Detection Kit. The intracetlular ROS levels were assessed using a 2, 7-dichlorofluorescein probe assay. The mitochondrial membrane potential was measured with the dual-emission potential-sensitive probe 5, 5＇, 6, 6＇-tetra-chloro-1, 1＇, 3, 3＇-tetraethyl-imidacarbocyanine iodide （JC-1）. The degradation of poly-ADP-ribose polymerase （PARP） protein, the phosphorylation of PKR-like ER kinase （PERK）, the phosphorylation of the a-subunit of eukaryotic initiation factor 2 （elF2a）, the expression of the 78 kD glucose-regulated protein （GRP 78）, and the activation of caspase-12 were analyzed via western blot analysis. Results ISL significantly inhibited the proliferation, the increase in ROS levels and apoptotic rates of HeLa cells in a concentration-dependent manner. Moreover, ISL induced mitochondrial dysfunction, caspase activation, and PARP cleavage, which displayed features of mitochondria dependent on apoptotic signals. Besides, exposure of HeLa cells to ISL triggered endoplasmic reticulum （ER） stress, as indicated by the increase in p-elF2a and GRP78 expression, ER stress-dependent apoptosis is caused by the activation of ER-specific caspase-12. Conclusion The findings from our study suggest that ISL-induced oxidative stress causes HeLa cel apoptosis via the mitochondrion-dependent and the ER stress-triggered signaling pathways.
基金supported by the National Key Research and Development Program of China(No.2020YFB1806000)。
文摘The high-speed movement of satellites makes it not feasible to directly apply the mature routing scheme on the ground to the satellite network.DT-DVTR in the snapshot-based connectionoriented routing strategy is one of the representative solutions,but it still has room for improvement in terms of routing stability.In this paper,we propose an improved scheme for connection-oriented routing strategy named the Minimal Topology Change Routing based on Collaborative Rules(MTCR-CR).The MTCR-CR uses continuous time static topology snapshots based on satellite status to search for intersatellite link(ISL)construction solutions that meet the minimum number of topology changes to avoid route oscillations.The simulation results in Beidou-3 show that compared with DT-DVTR,MTCR-CR reduces the number of routing changes by about 92%,the number of path changes caused by routing changes is about38%,and the rerouting time is reduced by approximately 47%.At the same time,in order to show our algorithm more comprehensively,the same experimental index test was also carried out on the Globalstar satellite constellation.
