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sagaman

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[交流] 南大新出两篇Science文章

Research Articles 封面文章
A Swimming Mammaliaform from the Middle Jurassic and Ecomorphological Diversification of Early Mammals
Qiang Ji,1,3 Zhe-Xi Luo,2,1* Chong-Xi Yuan,3 Alan R. Tabrum2
A docodontan mammaliaform from the Middle Jurassic of China possesses swimming and burrowing skeletal adaptations and some dental features for aquatic feeding. It is the most primitive taxon in the mammalian lineage known to have fur and has a broad, flattened, partly scaly tail analogous to that of modern beavers. We infer that docodontans were semiaquatic, convergent to the modern platypus and many Cenozoic placentals. This fossil demonstrates that some mammaliaforms, or proximal relatives to modern mammals, developed diverse locomotory and feeding adaptations and were ecomorphologically different from the majority of generalized small terrestrial Mesozoic mammalian insectivores.

1 Department of Earth Science, Nanjing University, Nanjing 200017, China.
2 Carnegie Museum of Natural History, Pittsburgh, PA 15213, USA.
3 Chinese Academy of Geological Sciences, Beijing 100037, China.

* To whom correspondence should be addressed. E-mail: LuoZ@CarnegieMNH.org

Reports
X-ray Flares from Postmerger Millisecond Pulsars
Z. G. Dai,1* X. Y. Wang,1 X. F. Wu,2 B. Zhang3
Recent observations support the suggestion that short-duration gamma-ray bursts are produced by compact star mergers. The x-ray flares discovered in two short gamma-ray bursts last much longer than the previously proposed postmerger energy-release time scales. Here, we show that they can be produced by differentially rotating, millisecond pulsars after the mergers of binary neutron stars. The differential rotation leads to windup of interior poloidal magnetic fields and the resulting toroidal fields are strong enough to float up and break through the stellar surface. Magnetic reconnection–driven explosive events then occur, leading to multiple x-ray flares minutes after the original gamma-ray burst.

1 Department of Astronomy, Nanjing University, Nanjing 210093, China.
2 Purple Mountain Observatory and Joint Center for Particle Nuclear Physics and Cosmology of Purple Mountain Observatory–Nanjing University, Chinese Academy of Sciences, Nanjing 210008, China.
3 Department of Physics, University of Nevada, Las Vegas, NV 89154, USA.

* To whom correspondence should be addressed. E-mail: dzg@nju.edu.cn

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