As described previously, cervical cancers are caused by infection with one of the high-risk HPV types. However, since not all people who are infected with HPV will develop cancer, it is likely that other factors also play a role in the development of cervical cancer.
ballast factor (BF) - The ratio of the light output of a fluorescent lamp or lamps operated on a ballast to the light output of the lamp(s) operated on a standard (reference) ballast. Ballast factor depends on both the ballast and the lamp type; a single ballast can have several ballast factors depending on lamp type. compact fluorescent lamp (CFL) - A family of single-ended fluorescent-discharge light sources with small-diameter [16-millimeter (5/8-inch) or less] tubes.
A ballast is any heavy material that helps to make a ship or plane stable, including metaphorical ships like your mood. If you hate school, the thought of a weekend coming might be a ballast for your mood. Ballast comes from old ship terminology for cargo. It came to mean the weight of the cargo that prevents the ship from rocking around on the open seas. Any craft, ship or plane, needs ballast.