function Ct = brix(p,t)
% Brix model see 
% Fusco et al. Journal of Biomedical Graphics and computing, 2(2);2012

A   = p(1); % mmol/L/min
kep = p(2); % min^-1
kel = p(3); % min^-1

Ct = (A / (kel - kep)) * (exp(-kep*t) - exp(-kel*t) );

Ct(t<0)=0; % before injection Ct is 0

endfunction

