Radiocarbon dating a third radiocarbon revolution. Occasionally, radiocarbon dating techniques date an object of popular interest, for example the Shroud of Turin, a piece of linen cloth thought by some to bear an image of Jesus Christ after his crucifixion. Three separate laboratories dated samples of linen from the Shroud in 1988; the results pointed to 14th-century origins, raising doubts about the shroud's authenticity as an alleged 1st-century relic. Researchers have studied other radioactive isotopes created by cosmic rays to determine if they could also be used to assist in dating objects of archaeological interest; such isotopes include , , , ,
Stable-isotope probing organisms were consuming existing carbohydrates and which were using carbohydrates more recently produced from photosynthesis. When DNA is the biomarker, SIP theoretically can be performed using isotopically labeled C, H, O or N, though C is used most often. Cupples et al. (2007) demonstrated a weaker DNA buoyant density shift in when N- versus C-labeled substrates were used in pure culture, conversely a very strong buoyant density shift was observed when both labels were used. Stable-isotope probing Stable-isotope probing (SIP) is a technique in microbial ecology for tracing fluxes of nutrients in biogeochemical cycling by microorganisms. A substrate is enriched