changes made:
1 layout customized to fit my usual design
2 change decay constant ?1= k1 and ?1= k2 to suit sg syllabus
3 added half life fields t1_1/2 = ln2/?1 and t2_1/2 = ln2/?2
4 added plot lines for ease of association to half life symbol t1/2 the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
5 added world view check-box so that the plot can be full screen view
6 relay the panel to allow any panel to be full screen view.