Multiplayer Homicidal Chauffeur reach-avoid games: a pursuit enclosure function approach

This paper presents a multiplayer Homicidal Chauffeur reach-avoid differential game, which involves Dubins-car pursuers and simple-motion evaders. The goal of the pursuers is to cooperatively protect a planar convex region from the evaders, who strive to reach the region. We propose a cooperative strategy for the pursuers based on subgames for multiple pursuers against one evader and optimal task allocation. We introduce pursuit enclosure functions (PEFs) and propose a new enclosure region pursuit (ERP) winning approach that supports forward analysis for the strategy synthesis in the subgames. We show that if a pursuit coalition is able to defend the region against an evader under the ERP winning, then no more than two pursuers in the coalition are necessarily needed. We also propose a steer-to-ERP approach to certify the ERP winning and synthesize the ERP winning strategy. To implement the strategy, we introduce a positional PEF and provide the necessary parameters, states, and strategies that ensure the ERP winning for both one pursuer and two pursuers against one evader. Additionally, we formulate a binary integer program using the subgame outcomes to maximize the captured evaders in the ERP winning for the pursuit task allocation. Finally, we propose a multiplayer receding-horizon strategy where the ERP winnings are checked in each horizon, the task is allocated, and the strategies of the pursuers are determined. Numerical examples are provided to illustrate the results

Effects of an immunosuppressive active component of Periplocae Cortex (Periploca sepium Bge.) on positive selection of thymocytes in vitro

Objective: To determine the effect of an immunosuppressive active component (periploside A) isolated from the stem bark of Periplocae Cortex (Periploca sepium Bge.), a Chinese medicinal herb used in the treatment of rheumatoid arthritis for centuries in China, on positive selection of thymocytes in vitro. Methods: Female C57BL/6 mice at 6 weeks of age were housed in specific pathogen-free conditions. Double-positive thymocytes from C57BL/6 mice were induced into positive selection in vitro with or without periploside A treatment. Cell viability and expression of CD69, CD4, and CD8 were analyzed by flow cytometry. Results: Flow cytometric examination of thymocyte populations revealed that the percentage of CD8+ single-positive thymocytes was decreased by periploside A upon differentiation induced by an anti-CD3 antibody. However, the percentage of CD4+ single-positive thymocytes was decreased by periploside A upon differentiation induced by phorbol 12-myristate 13-acetate/ionomycin. Expression of CD69 plays a major role in prohibiting differentiation of thymocytes. Treatment with periploside A decreased CD69 expression in thymocytes. Conclusion: These results demonstrate that periploside A influences positive selection of thymocytes in vitro. Keywords: Immunosuppressive active component, Positive selection, Thymocyte