Multi-ASV Collision Avoidance for Point-to-Point Transitions Based on Heading-Constrained Control Barrier Functions With Experiment

Dear Editor, Collision avoidance is critical for safe operations of multiple autonomous surface vehicles(ASVs). It is a challenging task to design collision-free control laws to ensure safety, especially in a crowded sea environment. This letter presents a collision-free pointto-point transition strategy for multiple ASVs subject to static obstacles, dynamic obstacles and neighboring ASVs based on control barrier functions(CBFs).

Safety-Critical Game-Based Formation Control of Underactuated Autonomous Surface Vehicles

Dear Editor,This letter addresses the noncooperative formation control of multiple underactuated autonomous surface vehicles (ASVs) in an obstacle-laden environment.Each ASV is subject to external disturbances and fully unknown model parameters.A safety-critical game-based formation control method is proposed such that the multiple AS Vs are able to track a reference trajectory,and accomplish each individual interest in safety behaviors simultaneously.The stability and safety analyses show that the closed-loop system is input-to-state stable (ISS),and the multi-ASV system is guaranteed for input-to-state safety (ISSf).Simulation results substantiate the proposed safety-critical game-based formation control method.

A paradox:Insulin inhibits expression and secretion of resistin which induces insulin resistance

AIM: To confirm whether insulin regulates resistinexpression and secretion during differentiation of 3T3-L1preadipocytes and the relationship of resistin with insulinresistance both in vivo and in vitro.METHODS: Supernatant resistin was measured duringdifferentiation of 3T3-L1 preadipocytes. L6 rat myoblastsand hepatoma cell line H4IIE were used to confirm thecellular function of resistin. Diet-induced obese ratswere used as an insulin resistance model to study therelationship of resistin with insulin resistance.RESULTS: Resistin expression and secretion wereenhanced during differentiation 3T3-L1 preadipocytes.This cellular differentiation stimulated resistin expressionand secretion, but was suppressed by insulin. Resistinalso induced insulin resistance in H4IIE hepatocytes andL6 myoblasts. In diet-induced obese rats, serum resistinlevels were negatively correlated with insulin sensitivity,but not with serum insulin.CONCLUSION: Insulin can inhibit resistin expressionand secretion in vitro, but insulin is not a major regulatorof resistin in vivo . Fat tissue mass affects insulinsensitivity by altering the expression and secretion ofresistin.

Verapamil inhibits 3T3-L1 preadipocyte differentiation

Objective： To investigate the effect of the calcium channel blocker verapamil on adipocyte differentiation and its mechanism of action. Methods： Preadipocytes from 3T3-L1 strain mouse embryos were cultured and differentiated into matured adipocytes in vitro. Verapamil was added to the culture medium in the concentration of 30 μmol/L on Day 0. Cell differentiation was determined by Oil Red O staining and marker gene mRNA expression was evaluated and compared by RT-PCR. The fluo-3/AM probe and laser scanning confocal microscopy were used to measure intracetlular calcium concentrations. Results： （1）The differentiation rate of 3T3-L1 preadipocytes exposed to verapamil was lower than that of untreated cells. （2）Verapamil promoted the retention of pref-1 gene expression. Lipoprotein lipase expression in the verapamil group was significantly lower than that in the control group on Day 4, Day 6 and Day 8 （P 〈 0.05） and resistin expression was significantly lower than that in the control group on Day 6, Day 8 and Day 10 （P 〈 0.05）. Fatty acid synthase expression in the verapamil group was significantly lower than that in the control group from Day 2 （P 〈 0.05）. （3） Intracellular concentrations of calcium [Ca^2＋]i in the verapamil group were significantly decreased compared with those in the control group on Day 2, Day 4 and Day 6 （P 〈 0.05）, while there was no obvious difference between the two groups on Day 0 （P 〉 0.05）. Conclusion： In 3T3-L1 preadipocytes verapamil significantly reduced adipocyte differentiation, down-regulated the mRNA expression of three marker genes for adipocytes differentiation, and prolonged the mRNA expression of an inhibitor of differentiation. The inhibitory effect of verapamil on differentiation may involve its role as a blocker of calcium influx in adipocytes.