%% %%%%%% MATLAB ODE Simulation of the Budding Yeast Cell Cycle %%%%%% %%
% The ODE model is taken from Chen(2004): 
% Chen, K.C. and Calzone, L. and Csikasz-Nagy, A. and Cross, F.R. and
% Novak, B. and Tyson, J.J. 2004. Integrative analysis of cell cycle 
% control in budding yeast, Molecular Biology of the Cell 15:3841-3862
% The equations and parameters were downloaded from
% http://mpf.biol.vt.edu/research/budding_yeast_model/model_download/bychen04.ode
% and converted into MATLAB code by Kartik Subramanian (VirginiaTech) and
% Kamaludin Dingle (Oxford Univ.). September 2010.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% GK.m %%
% This function simply evaluates the formula for GK, as defined in Chen(2004)

function gk = GK(Va,Vi,Ja,Ji)
BB = Vi-Va+Ja*Vi+Ji*Va;
gk = 2*Ji*Va/(BB+sqrt(BB^2-4*(Vi-Va)*Ji*Va));