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Abstract Coral reefs are increasingly experiencing stressful conditions, such as high temperatures, that cause corals to undergo bleaching, a process where they lose their photosynthetic algal symbionts. Bleaching threatens both corals’ survival and the health of the reef ecosystems they create. One possible mechanism for corals to resist bleaching is through association with stress-tolerant symbionts, which are resistant to bleaching but may be worse partners in mild conditions. Some corals have been found to associate with multiple symbiont species simultaneously, which potentially gives them access to the benefits of both stress-sensitive and -tolerant symbionts. However, within-host competition between symbionts may lead to competitive exclusion of one partner, and the consequences of associating with multiple partners simultaneously are not well understood. We modify a mechanistic model of coral-algal symbiosis to investigate the effect of environmental conditions on within-host competitive dynamics between stress-sensitive and -tolerant symbionts and the effect of access to a tolerant symbiont on the dynamics of recovery from bleaching. We found that the addition of a tolerant symbiont can increase host survival and recovery from bleaching in high-light conditions. Competitive exclusion of the tolerant symbiont occurred slowly at intermediate light levels. Interestingly, there were some cases of post-bleaching competitive exclusion after the tolerant symbiont had helped the host recover. 

This paper discusses the implementation of Industry 4.0 in an educational setting. Simulation, virtual reality, analytics, robotics and automation, and 3D printing are integrated to develop a small-scale production line for producing and inspecting 3D printed parts. The system consists of a robot and controller, programmable logic controller, 3D printer, machine vision system, conveyor belt, 3-phase motor and motor controller, webcam, PC and monitor, Raspberry Pi computer, pneumatic system, beam sensor, simulation software, and VR equipment. The system components are connected via ethernet cables running to a basic ethernet switch. An ethernet router is also connected to the switch to resolve IP connection attempts by the connected components. A mini CNC machine is used to drill holes on small metal parts that are assembled with 3D printed parts and plastic bricks to make a car toy. A robot is pre-programmed to perform the assembly of the car toy and a Cognex® camera is used to inspect the parts. Deep learning models are used to predict the remaining useful life of the drilling bits.