The half-life of a radioactive element is $10 \ h$. The fraction of initial radioactivity of the element that will remain after $40 \ h$ is

During joint diastole,..........

In the given figure,what do $A$ and $B$ represent respectively?

$\frac{{\sqrt{2} - \sin \alpha - \cos \alpha }}{{\sin \alpha - \cos \alpha }} = $

$A$ body is thrown vertically upwards and reaches its maximum height in $t$ seconds. The total time from the time of projection to reach a point at half of its maximum height while returning (in seconds) is:

What are the substances which mimic the natural chemical messengers?