In a normal demand DielsâAlder reaction, the dienophile has an electron-withdrawing group in conjugation with the alkene; in an inverse-demand scenario, the dienophile is conjugated with an electron-donating group.Dienophiles can be chosen to contain a masked functionality.n a normal demand DielsâAlder reaction, the dienophile has an electron-withdrawing group in conjugation with the alkene; in an inverse-demand scenario, the dienophile is conjugated with an electron-donating group.
A standard echocardiogram or a fetal echocardiogram test usually takes about 30 to 60 minutes. A stress echocardiogram usually takes between 60 and 90 minutes.
Patients included in the study were HMO members 20 years and older who had an echocardiogram and a diagnosis of heart failure between 1999 and 2004; they were followed for up to one year post echocardiogram (or until April 1, 2005, death, or disenrollment from the health plan, whichever came first).