These industries create long chains of backward linkages. Food webs depict energy flow via trophic linkages. The skeletons of robotic systems are examples of spatial linkages. Modern machine theory analyzes machines as kinematic chains composed of elementary linkages called kinematic pairs. Servo savers are integrated into all steering linkages and some nitro throttle linkages. Rag joints are commonly used on automotive steering linkages and drive trains. Steering is the collection of components, linkages, etc. PLGA degrades by hydrolysis of its ester linkages in the presence of water. Carboxypeptidase cleaves peptide linkages during digestion of proteins. Originally, engine control systems consisted of simple mechanical linkages connected physically to the engine. It also needs to focus on the interpersonal linkages in the team. This is typically achieved by a series of linkages, rods, pivots and gears. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics. Often both functions are combined in a set of linkages. This applies to all mechanical systems ranging from robots to linkages.