1 Routine screening of average-risk women should begin at age 50, instead of age 40. 2  Routine screening should end at age 74. 3  Women should get screening mammograms every two years instead of every year.4  Breast self-exams have little value, based on findings from several large studies. Routine screening of average-risk women should begin at age 50, instead of age 40. 2  Routine screening should end at age 74. 3  Women should get screening mammograms every two years instead of every year.
in chemical compound: Alkynes. Molecules that contain a triple bond between two carbon atoms are known as alkynes. The triple bond is made up of one Ï bond and two Ï bonds. As in alkenes, the Ï bonds constitute regions of increased electron density lying parallel to the carbon-carbon bond axis.
An alkyne is a molecule made up entirely of carbon and hydrogen where on or more carbon atoms are connected by triple bonds. The general formula for an alkyne is CnH2n-2 where n is the number of carbon atoms in the molecule. Alkanes are named by adding the -yne suffix to the prefix associated with the number of carbon atoms present in the molecule. A number and dash before the name denotes the number of the carbon atom in the chain that begins the triple bond.