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 hydrocarbon containing a carbonâcarbon triple bond; the simplest member ofthis family is acetylene, HLC'CLH. The chemistry of the carbonâcarbon triple bond issimilar in many respects to that of the carbonâcarbon double bond; indeed, alkynes andalkenes undergo many of the same addition reactions.he sufï¬x ane in the name of the corresponding alkane is replaced by the sufï¬x yne, and the triple bond is given the lowest possible number.Substituent groups that contain a triple bond (called alkynyl groups) are named by replac-ing the ï¬nal e in the name of the corresponding alkyne with the sufï¬x yl.