On the other hand, batteries have low energy densities, short service life, poor performance at extreme temperatures, long charging times, and difficulties with disposal (although they can usually be recycled). Like fuel, batteries store chemical energy and can cause burns and poisoning in event of an accident. Batteries also lose effectiveness with time. The issue of charge time can be resolved by swapping discharged batteries with charged ones; however, this incurs additional hardware costs and may be impractical for larger batteries. Moreover, there must be standard batteries for battery swapping to work at a gas station. Fuel cells are similar to batteries in that they convert from chemical to electrical energy, but have their own advantages and disadvantages. Electrified rails and overhead cables are a common source of electrical energy on subways, railways, trams, and trolleybuses. Solar energy is a more modern development, and several solar vehicles have been successfully built and tested, including Helios, a solar-powered aircraft. Nuclear power is a more exclusive form of energy storage, currently limited to large ships and submarines, mostly military. Nuclear energy can be released by a nuclear reactor, nuclear battery, or repeatedly detonating nuclear bombs. There have been two experiments with nuclear-powered aircraft, the Tupolev Tu-119 and the Convair X-6. Mechanical strain is another method of storing energy, whereby an elastic band or metal spring is deformed and releases energy as it is allowed to return to its ground state.
Retrobulbar bleeding, also known as retrobulbar hemorrhage, is when bleeding occurs behind the eye. Symptoms may include pain, bruising around the eye, the eye bulging outwards, vomiting, and vision loss.Retrobulbar bleeding can occur as a result of trauma to the eye, surgery to the eye, blood thinners, or an arteriovenous malformation.In those with significant symptoms lateral canthotomy with cantholysis is indicated. This is recommended to be carried out within two hours. The condition is rare. == References ==