dx1/dt = -b*x1*x7*x3*q - b*x1*x7*x4 - b*x1*x7*x5;
dx2/dt = b*x1*x7*x3*q + b*x1*x7*x4 + b*x1*x7*x5 - x2*k;
dx3/dt = -x2*k*r + x2*k - x3*g1;
dx4/dt = -alpha*x4 + x2*k*r - g1*x4;
dx5/dt = alpha*x4 - g2*x5;
dx6/dt = alpha*x4;
dx7/dt = 0;
y1 = x6;
y2 = x7
