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.
Ballast is the main ingredient in concrete and is a proportional mixture of sharp sand and aggregate. Concrete is made up of 4 parts aggregate, 2 parts sharp sand, 1 part cement and water.The bit that is aggregate and sharp sand is known collectively as as 'ballast' and is sold as such ready-mixed in tonne bags etc.hirdly ballast is a sand and stones/chips mix, typically 10mm to 20 mm size stones.Mix this with cement and you get concrete.