Co 3 O 4 with high capacities and energy density has potential applications to be electrode materials for lithium ion batteries, one of the most important power sources. For improving the cycling stability, the Co 3 O 4 nanostructures are required. Herein, we report successful construction of Co 3 O 4 hexagonal nanorings and nanoplates/nanoparticles via treating Co-based metal organic frameworks (MOFs) with organic amine. The studies show that the release rate of Co(II) to the reaction system and the spatial hindrance of the organic linkers of MOFs determine the final morphology of Co 3 O 4 . As an anode for lithium ion batteries, Co 3 O 4 hexagonal nanorings with 1370 mA h g À1 specific capacity after 30 cycles displayed higher reversible capacity and better stability than commercial Co 3 O 4 particles with only 117 mA h g À1 specific capacity after 30 cycles. The improved performance of Co 3 O 4 hexagonal nanorings could be attributed to the shortened transfer path for Li + afforded by the special morphology.It is expected that plentiful metal oxide nanostructures could be constructed from MOFs due to the available versatile categories of MOFs.

a b s t r a c tThe question which type of signals can be determinately related to catastrophic rupture in heterogeneous brittle media still remains open. Here we report a specific precursor of catastrophic rupture, i.e. a power-law singularity of responses, based on rock experiments. Our experimental observations show that the singularity with power exponent À b, where b¼0.5170.10 (mean 7 s.d.), appears ahead of catastrophic rupture in some rocks, and the singularity does not appear at all for gradual failure. It is indicated that the power-law singularity can emerge well only close to catastrophic rupture and thus it could serve as a specific warning for catastrophic rupture. To address the potential forewarning of imminent catastrophic rupture, a fitting process based on the data before catastrophic rupture was developed to determine the two unknowns related to the occurrence, catastrophe point U F and the power exponent À b u . It is demonstrated that the power-law singularity appears only in the vicinity of catastrophe, and that the power-law singularity does not occur for gradual failure.

ZnO and Co3O4 in the interface of zinc–cobalt oxides work in a cooperative way as a water adsorption site and water oxidation site, respectively.

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Within the Geophysical Fluid Dynamics Laboratory Climate Model version 2p1 (GFDL CM2p1) coupled model, we find that the winter predictability barrier (WPB) exists in both the growing and decaying phases of positive Indian Ocean dipole (IOD) events, due to the effects of initial errors. The physical mechanism of the WPB, in which the initial errors show a significant seasonal-dependent evolution with the fastest error growth in winter, is explored from the dynamical and thermodynamical viewpoints. In terms of dynamics, in the growing phase of pure positive IOD events, the vertical temperature advection associated with the reference state IOD events plays a dominant role in advancing the fastest error growth in winter; in terms of thermodynamics, the latent heat flux error and the shortwave radiation error lead to the fastest error growth in winter and favor the occurrence of the WPB. In the decaying phase of pure positive IOD events, the occurrence of the WPB is mainly due to the latent heat flux error since the dynamics play an insignificant role in advancing the fast error growth in winter. For positive IOD events accompanied by El Niño-Southern Oscillation (ENSO), the physical mechanism of the WPB is similar to that for pure positive IOD events in both the growing and decaying phases, except that the shortwave radiation error has a different effect on the error growth in winter, which may be closely related to the perturbed atmospheric circulation in the tropical Indian Ocean associated with ENSO.

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