Method and apparatus for detecting, by absorption spectroscopy, an isotopic ratio of a sample, by passing first and second laser beams of different frequencies through the sample. The cross-talk gain parameter can be optimized such that the effects of a perturbation applied to the tracking servo loop on an adjusted focus error signal, i. The transgenic knockout mouse with a homozygous FcRn disruption is also unable to absorb maternal IgG in the prenatal or neonatal stage of development. A link confidence code is subsequently determined for the customer based on a score generated by the scores used to define the match confidence code for each relationship in the set of relationships and on internal data associated with each relationship in the set of relationships.