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This study investigates the sampled-data containment control problem for linear multi-agent systems with multiple leaders under undirected or directed network topology. First, by means of the decomposition method, the containment control problem is transformed into the simultaneous stability analysis issue of certain subsystems. Then, the solution of a class of differential equations, which plays a key role for the addressed problem, is exploited by using the contradiction method. Together with a novel Lyapunov function, sufficient conditions are established to guarantee that all the followers move into the convex hull spanned by the leaders. The proposed results are dependent on the information of the system dynamics, the coupling strength as well as the eigenvalues of topology matrix. Furthermore, the established results are specialised to both the leader--following case and the traditional consensus case. Finally, simulations are given to illustrate the theoretical results derived in this study. [ABSTRACT FROM AUTHOR]

In this study, the stochastic sampled-data approach is developed to deal with the H∞ control problem for a class of linear multi-agent systems. For each agent, signals should be transmitted to the control input, including not only its own measurements, but also the output information received from the neighbour agents. The relationships of information communications between the whole multi-agents are totally reflected by a weighted directed graph with a fixed topology structure. To the addressed problem, the author's focus is to design an output feedback controller for each agent such that, for the external energy bounded disturbances, the exponential stability in the mean square sense and interference rejection ability under consideration can be guaranteed. By assuming that the sampling period of each agent switches between two values in a probabilistic way, the stochastic sampling phenomenon is well characterised in every sampling tasks. In virtue of Lyapunov theory and semi-definite programming method, sufficient conditions are derived to ensure the exponential stability as well as H∞ performance, and the feedback controllers are also designed by solving some certain matrix inequalities. Finally, a numerical simulation is given to demonstrate the validness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) are well known to have the capability to form bone and cartilage, and chondrogenesis derived from MSCs is reported to be affected by mechanical stimuli. This research was aimed to study the effects of cyclic compressive stress on the chondrogenic differentiation of rat bone marrow-derived MSCs (BMSCs) which were encapsulated in alginate scaffolds and cultured with or without chondrogenic medium, and to investigate the role of p38 MAPK phospho-relay cascade in this process. The results show that the gene expression of chondrocyte-specific markers of Col2α1, aggrecan, Sox9, Runx2, and Ihh was upregulated by dynamic compressive stress introduced at the 8th day of chondrogenic differentiation in vitro. The p38 MAPK was activated by chondrogenic cytokines in a slow and lagged way, but activated by cyclic compressive stimulation in a rapid and transient manner. And inhibition of p38 activity with SB203580 suppressed gene expression of chondrocyte-specific genes stimulated by chondrogenic medium and (or) cyclic compressive stress. These findings suggest that p38 MAPK signal acts as an essential mediator in the mechano-biochemical transduction and subsequent transcriptional regulation in the process of chondrogenesis. J. Cell. Physiol. 221: 609–617, 2009. © 2009 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]