The magnesium-to-calcium (Mg/Ca) ratio of coral skeletons from Ishigaki Island, Ryukyu Islands, Japan, closely tracked sea surface temperature (SST) over an 8-year period. Measurements were made with the fast technique of inductively coupled plasma-atomic emission spectrometry. The variation of the coral Mg/Ca ratio with SST change is about four times that of the current, widely used coral strontium-to-calcium ratio. The temporal and geographic variation of the seawater Mg2+/Ca2+ ratio probably has little influence on coral Mg/Ca variation. Results indicate that the coral Mg/Ca ratio has the potential to provide fast, precise, high-resolution proxies for past tropical SSTs.

We have developed a method of graphitization from CO2 samples for accurate 14C measurements by accelerator mass spectrometry. Our batch method, using a sealed Vycor tube, reduces the risk of contamination during graphitization and makes it possible to prepare many samples in a short time (typically 20 samples per day).

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The utility of DCP for the diagnosis of HCC was lower than that of AFP for small tumors, but higher than that of AFP for large tumors.

The weight ratio of total organic carbon to total nitrogen (C/N ratio) in 20 meters of sediment core from Nakaumi Lagoon (coastal brackish lake), Japan is examined for its suitability as an organic source indicator. The C/N ratio depth profile is compared to the depth profiles of other proxies, i.e., weight ratio of total organic carbon to total organic nitrogen (C/N org. ratio), stanol compositions, n-alkane compositions and the hydrogen-index by Rock-Eval pyrolysis.The C/N ratios of the lagoonal sediments, which have been deposited over the last ca. 8,000 years, have a different profile from that of the C/N org. ratio and other proxies due to the effects of a constant level of inorganic nitrogen (N inorg. : ca. 0.04%) in the sediments. When C org. content is less than 1 wt%, the presence of N inorg. lowers the C/N ratio considerably, giving an inaccurate indication of organic source. C-N and C/N ratio-C org. plots are useful for evaluating the effect of N inorg. ; if the depth profiles of the C/N ratio and C org. content exhibit similar trends, this is taken as a warning that the apparent variation in the C/N ratio should be carefully examined in conjunction with the other plots and proxies. It is also found that the C/N org. ratio itself also tends to increase due to the preferential decomposition of nitrogen compounds, and that in sediments containing high proportions of planktonic organic matter (OM), the sensitivity of the C/N ratio to changes in the proportions of planktonic-terrestrial OM is relatively low. lignin phenols, are not easily analyzed due to chemical complexity. Hence, the C/N ratio, having recently become easier to obtain through the popularization of rapid elemental analysis techniques, appears to be an effective and simple indicator of organic source, particularly in lacustrine depositional environments, including estuaries.The C/N ratio in aquatic systems is governed by the mixing of terrestrial and autochthonous OM