Function hc_wm_r2prime 

fn hc_wm_r2prime(theta: f64, mwf: f64, tes: &[f64], b0: f64) -> f64

Mono-exp-equivalent reversible rate the beat itself contributes (Hz): weighted-LS slope of log(|GRE|/SE) vs centred TE, negated and clamped ≥ 0.