Function Description
********************

	Name: R2_DIMER 
	Function: R2obs = fM * R2M + 2 * fD * R2D  
	Parameters: Kdimer R2dimer R2monomer

Notes
*****
	Fit of R2 relaxation data or chemical shift data to a
	monomer-dimer equilibrium as a function of total protein
	concentration where:

	P + P  <-> P:P; [P][P]/[P:P] = Kdimer
	R2obs = fM * R2M + 2 * fD * R2D 

	Function is undefined at x=0.

	Olga's derivation of the function is available as a ms word document on
	the website or lib/docs directory.

C-code for the function
***********************

	b = R2dimer - R2monomer;
	c = 4.0 * R2dimer * x;
	d = sqrt(Kdimer) * (R2monomer - R2dimer) * sqrt(Kdimer + 8.0 * x);
	answer = ((Kdimer * b) + c + d) / (4.0 * x);