Single-phase generator The early generators for those single-phase traction networks are single-phase generators. Even with newer three-phase motors which were introduced to some modern trains, the single-phases transmission for traction networks survive their time and are still in use in many railways today. However, many traction power stations have replaced their generators over time to use three-phase generators and convert into single-phase for transmission. In the early development of hydroelectricity, single-phase generators played an important role in demonstrating the benefits of alternating current. In 1891, a 3,000 volts and 133 Hz single-phase generator of 100 horsepower was installed at Ames Hydroelectric Generating
Single-use bioreactor conventional bioreactors. Instead of a culture vessel made from stainless steel or glass, a single-use bioreactor is equipped with a disposable bag. The disposable bag is usually made of a three-layer plastic foil. One layer is made from Polyethylene terephthalate or LDPE to provide mechanical stability. A second layer made using PVA or PVC acts as a gas barrier. Finally, a contact layer is made from PVA or PP. For medical applications the single-use materials that contact the product must be certified by the European Medicines Agency or similar authorities responsible for other regions. In general there are two different