dx1/dt=-d1*x1-d2*x1*x3;
dx2/dt=kTL*x1-b*x2;
dx3/dt=d3*x4-d2*x1*x3;
dx4/dt=-d3*x4+d2*x1*x3;
y1=x2;
x1(0)=1;
x2(0)=0;
x3(0)=1;
x4(0)=0
