Anywhere there is a potential for contamination or pollution of the drinking water system, a backflow prevention device is required. Devices can be small and simple, such as an anti-siphon vacuum breaker (AVB) on a hose spigot (Photo), or large and complex, like those used on fire sprinkler systems (Photo).
An avulsion fracture occurs when a muscle or tendon is pulled so hard at the spot where it attaches to the bone that it tears a small piece of bone away. Avulsion fractures can occur on any part of the body, but they are most common in the ankles, hips, and elbows.
From a purely thermodynamic point of view, an emulsion is an unstable system because there is a natural tendency for a liquid/liquid system to separate and reduce its interfacial area and, hence, its interfacial energy.