Many nebulae or stars form from the gravitational collapse of gas in the interstellar medium or ISM. As the material collapses under its own weight, massive stars may form in the center, and their ultraviolet radiation ionizes the surrounding gas, making it visible at optical wavelengths.he size of these nebulae, known as HII regions, varies depending on the size of the original cloud of gas. New stars are formed in the nebulae. The formed stars are sometimes known as a young, loose cluster. Some nebulae are formed as the result of supernova explosions, the death throes of massive, short-lived stars.
In addition, one vaccine for the prevention of H5N1 influenza, commonly referred to as avian influenza or âbird flu,â contains the adjuvant AS03, an oil-in-water emulsion.
Like all seasonal flu vaccines, vaccines that protect against four flu viruses will be monitored for their safety and effectiveness. Quadrivalent vaccine cannot cause influenza illness, because the vaccine viruses used to make it are âinactivatedâ (killed) or attenuated (weakened).he quadrivalent flu vaccine is designed to protect against four different flu viruses; two influenza A viruses and two influenza B viruses.