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.
Alkynes have less hydrogen atoms than alkanes and alkenes. C 2 H 2 CH CH C 3 H 4 CH C-CH 3 Naming unbranched alkenes and alkynes: we use the IUPAC system of naming for alkanes. For alkenes, we replace the suffix â-aneâ of alkanes by â -ene â. For alkynes, we replace the suffix â-aneâ of alkanes by â -yne â.