The event Permian-Triassic boundary (EPTB) is well marked by the famous 'white clay' of bed 25 in Mei-shan Section located in Changxing county, Zhejiang province of China. In this note, the white clay as well ...The event Permian-Triassic boundary (EPTB) is well marked by the famous 'white clay' of bed 25 in Mei-shan Section located in Changxing county, Zhejiang province of China. In this note, the white clay as well as its overlying and underlying sequences is investigated particularly for mineralogical records. The investigation yields three findings that contribute to better understanding the scenario of the EPTB mass extinction. (i) A red goethite-rich microlayer (0.3 mm) is first recognized to be horizontally widespread on the base of the white clay in the section. The microlayer should be considered as a macro geochemical indicator naturally tracing a catastrophic initiation at the EPTB. (ii) An interruption of marine carbonate deposition is discovered due to blank of carbonate minerals in the white clay. The discovery provides significant evidence of a marine acidification event that would occur in the paleo-ocean with marine acidity estimated at pH【4.0 at least and be triggered by the ultimate展开更多
In this paper, we extend Parikh＇ recent work to the Vaidya-de Sitter black hole which is non-stationary. We view Hawking radiation as a tunnelling process across the event horizon and calculate the tunnelling probabi...In this paper, we extend Parikh＇ recent work to the Vaidya-de Sitter black hole which is non-stationary. We view Hawking radiation as a tunnelling process across the event horizon and calculate the tunnelling probability when the particle crosses the event horizon. From the tunnelling probability we also find a leading correction to the semiclassical emission rate.展开更多
基金This work was partly supported by the National Natural Science Foundation of China (Grant Nos. 40072055 and 40043010).
文摘The event Permian-Triassic boundary (EPTB) is well marked by the famous 'white clay' of bed 25 in Mei-shan Section located in Changxing county, Zhejiang province of China. In this note, the white clay as well as its overlying and underlying sequences is investigated particularly for mineralogical records. The investigation yields three findings that contribute to better understanding the scenario of the EPTB mass extinction. (i) A red goethite-rich microlayer (0.3 mm) is first recognized to be horizontally widespread on the base of the white clay in the section. The microlayer should be considered as a macro geochemical indicator naturally tracing a catastrophic initiation at the EPTB. (ii) An interruption of marine carbonate deposition is discovered due to blank of carbonate minerals in the white clay. The discovery provides significant evidence of a marine acidification event that would occur in the paleo-ocean with marine acidity estimated at pH【4.0 at least and be triggered by the ultimate
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10373003, 10475013 and the State Key Development for Basic Research of China （Grant No 2003CB716300）.Acknowledgement We would like to thank Guihua Tian for help.
文摘In this paper, we extend Parikh＇ recent work to the Vaidya-de Sitter black hole which is non-stationary. We view Hawking radiation as a tunnelling process across the event horizon and calculate the tunnelling probability when the particle crosses the event horizon. From the tunnelling probability we also find a leading correction to the semiclassical emission rate.
