Spalding and colleagues used the rise in atmospheric carbon-14 from nuclear weapons testing, which declined after 1963 and is recorded in genomic DNA, to date when human cells were born; neurons in the adult occipital cortex were as old as the person, while non-neuronal cells were replaced.
As reported in: Spalding, Bhardwaj, Buchholz et al. (2005). Retrospective Birth Dating of Cells in Humans. Cell. doi:10.1016/j.cell.2005.04.028
Spatzal and colleagues used atomic-resolution X-ray data and spin-echo spectroscopy to show that the light atom at the centre of nitrogenase's iron-molybdenum (FeMo) cofactor is a carbon species.
As reported in: Spatzal, Aksoyoglu, Zhang et al. (2011). Evidence for Interstitial Carbon in Nitrogenase FeMo Cofactor. Science. doi:10.1126/science.1214025
Arnold and Libby checked age determinations from radiocarbon content against samples of known age.
As reported in: Arnold, Libby (1949). Age Determinations by Radiocarbon Content: Checks with Samples of Known Age. Science. doi:10.1126/science.110.2869.678