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An Access Control Mechanism based on Permission Delegation in P2P Network
ZHANG Changyou,LIU Renfen,CAO Yuanda,LI Yanhua,CUI Liang 보안공학연구지원센터 2008 International Journal of Security and Its Applicat Vol.2 No.2
P2P(Peer-to-Peer) is a popular model in distributed computing. We present an access control mechanism based on permission delegation in this paper. This mechanism consists of three protocols, i.e. agency discovering protocol, permission delegating protocol and resource access protocol. Firstly, the task initiator decomposes the task into subtasks and chooses other peers in high trust degree with satisfied abilities to accomplish these subtasks. We call these neighbors as task agents. Then task initiator temporarily transfers some necessary permission to subtask agents by means of credit certificate and delegation certificate. Finally, the subtask agents consume resources of resource peers followed access protocol. These protocols are analyzed in Colored Petri-Net, and simulated with CPN Tools.
Croton Tiglium Extract Induces Apoptosis via Bax/Bcl-2 Pathways in Human Lung Cancer A549 Cells
Li, Changyou,Wu, Xiao,Sun, Rongli,Zhao, Peng,Liu, Fengjuan,Zhang, Chunling Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.11
Objective: To investigate the impact of a Croton tiglium extract on cellular proliferation and apoptosis in a non-small cell lung cancer cell line (A549) in vitro. Methods: A Croton tiglium seed methanol extract was prepare and assessed for effects on A549 cells regarding cellular proliferation, apoptotic rates, and expression of apoptosis related genes and proteins using real-time PCR and immunofluorescence. Results: The tested Croton tiglium extract inhibited A549 cell proliferation in a dose- and time-dependent manner, with significant elevation of apoptotic indexes at various concentrations after 24 h. In addition, rates in both early and late stages were higher in treated than untreated groups, the $100{\mu}g/ml$ dose causing the highest levels of apoptosis. RT-PCR showed that A549 cells treated with $100{\mu}g/ml$ Croton tiglium extract for 24 h has markedly higher Bax mRNA expression levels and obviously lower Bcl-2 expression levels than controls, equivalent results being observed for proteins by immunofluorescence. However, the mRNA expression levels of Fas and caspase-8 were not significantly altered. Conclusion: A Croton tiglium extract can inhibit proliferation of A549 cells and promote apoptosis though Bax/Bcl-2 pathways.
Polycaprolactone Scaffold Modified with Galactosylated Chitosan for Hepatocyte Culture
Yuan Qiu,Changyou Gao,Zhengwei Mao,Yimu Zhao,Jichuan Zhang,Qi Guo,Zhongru Gou 한국고분자학회 2012 Macromolecular Research Vol.20 No.3
A suitable extracellular matrix that can maintain long-term proliferation and liver-specific functions of hepatocytes is essential for both extracorporeal bioartificial liver (BAL) assist systems and implantable cell-scaffold constructs. In this work, a polycaprolactone (PCL) scaffold was modified with galactosylated chitosan (GC) to achieve better bioactivity and mechanical stability. The PCL scaffold, prepared by a method of gelatin particle leaching,was hydrolyzed to produce carboxylic groups that were utilized to react with the amine groups of the GC, which was synthesized by grafting the galactose to chitosan. Results showed that the content of carboxylic groups was increased initially with the hydrolysis time until 10 min, at which a COOH density of 2.0×10-5 mol/mg scaffold was reached. The incorporated GC amount showed a positive relationship with the COOH density and finally reached a 100 μg/mg scaffold with a hydrolysis time of 15 min. The incorporated GC was rather stable against incubation in the medium, and could significantly enhance the compression strength of the PCL scaffold in a wet state. With the galactose ligands on the surface, the PCL scaffold could be better recognized by hepatocytes, and show better cell viability, spheroid formation and long-term maintenance of liver-specific functions such as albumin secretion.