new examples & smoke tests: Gedzelman & Arnold 1994 fig 2, Miyake et al. 1968 fig 19; isotope diffusivity ratios in Formulae (Graham's law; Stewart 1975; Hellmann & Harvey); isotope relaxation timescales formulae (Miyake); new ventilation test based on Kinzer & Gunn 1951 table 1; null refactor in Formulae; access to RogersYau terminal vel. from Formulae

new examples & smoke tests: Gedzelman & Arnold 1994 fig 2, Miyake et al. 1968 fig 19; isotope diffusivity ratios in Formulae (Graham's law; Stewart 1975; Hellmann & Harvey); isotope relaxation timescales formulae (Miyake); new ventilation test based on Kinzer & Gunn 1951 table 1; null refactor in Formulae; access to RogersYau terminal vel. from Formulae #1873