Applications
Perforation frequently refers to the practice of creating a long series of holes or slits so that paper or plastics can be torn more easily along a given line: this is used in easy-open packaging. Since the creation of perforation devices in the 1840s and 1850s, it has seen use in several areas. Postage stamps are one common application of this, where small round holes are cut in lines to create individual pieces. Perforations on stamps are rather large, in the order of a millimeter, in comparison other perforated materials often have smaller holes. It is common for cheque-books, notebooks and legal pads to have perforations making it easier to tear out individual pages or leaves. Perforation is used in ways to separate loose leaf (or even a form of graph paper from a ringed binder). A fine perforation next to the rings allows the page to be separated from the book with no confetti. Screwcaps on glass or plastic bottles are sealed with a ring at the bottom of the cap attached by perforation. Twisting the cap has the effect of rupturing the material between the perforations and indicating that the original seal has been broken. The edges of film stock are perforated to allow it to be moved precise distances at a time continuously. Similarly, punched cards for use in looms and later in computers input and output devices in some cases were perforated to ensure correct positioning of the card in the device, and to encode information.
Calfactant, also known as Infasurf, is an intratracheal suspension derived from the natural surfactant in calf lungs. It is used in premature infants with lung surfactant deficiency that causes infant respiratory distress syndrome (IRDS). Mechanism of action
Lung surfactant is essential for effective ventilation as it modifies alveolar surface tension. IRDS is caused by a lung surfactant deficiency. Calfactant serves as a substitute for the natural surfactant. == References ==