After the discovery of fullerene-C60, it took almost two decades for the possibility of boron-based fullerene structures to be considered. So far, there has been no experimental evidence for these nanostructures, in spite of the progress made in theoretical investigations of their structure and bonding. Here we report the observation, by photoelectron spectroscopy, of an all-boron fullerene-like cage cluster at B40(-) with an extremely low electron-binding energy. Theoretical calculations show that this arises from a cage structure with a large energy gap, but that a quasi-planar isomer of B40(-) with two adjacent hexagonal holes is slightly more stable than the fullerene structure. In contrast, for neutral B40 the fullerene-like cage is calculated to be the most stable structure. The surface of the all-boron fullerene, bonded uniformly via delocalized σ and π bonds, is not perfectly smooth and exhibits unusual heptagonal faces, in contrast to C60 fullerene.

Sodium layered transition metal oxides have been considered as promising cathode materials for sodium ion batteries due to their large capacity and high operating voltage. However, mechanism investigations of chemical evolution and capacity failure at high voltage are inadequate. As a representative cathode, Na 2/3 Ni 1/3 Mn 2/3 O 2 , the capacity contribution at a 4.2 V plateau has long been assigned to the redox of the Ni 3+ /Ni 4+ couple, while at the same time it suffers large irreversible capacity loss during the initial discharging process. In this work, we prove that the capacity at the 4.2 V plateau is contributed to the irreversible O 2− /O 2 n− /O 2 evolution based on in situ differential electrochemical mass spectrometry and density functional theory calculation results. Besides, a phenomenon of oxygen release and subsequent surface lattice densification is observed, which is responsible for the large irreversible capacity loss during the initial cycle. Furthermore, the oxygen release is successfully suppressed by Fe substitution due to the formation of a unique Fe-(O−O) species, which effectively stabilizes the reversibility of the O 2− /O 2 n− redox at high operating voltage. Our findings provide a new understanding of the chemical evolution in layered transition metal oxides at high operating voltage. Increasing the covalency of the TM−O bond has been proven to be effective in suppressing the oxygen release and hence improving the electrochemical performance.

SUMMARYThis paper presents a novel computational approach, the discrete singular convolution (DSC) algorithm, for analysing plate structures. The basic philosophy behind the DSC algorithm for the approximation of functions and their derivatives is studied. Approximations to the delta distribution are constructed as either bandlimited reproducing kernels or approximate reproducing kernels. Uniÿed features of the DSC algorithm for solving di erential equations are explored. It is demonstrated that di erent methods of implementation for the present algorithm, such as global, local, Galerkin, collocation, and ÿnite di erence, can be deduced from a single starting point. The use of the algorithm for the vibration analysis of plates with internal supports is discussed. Detailed formulation is given to the treatment of di erent plate boundary conditions, including simply supported, elastically supported and clamped edges. This work paves the way for applying the DSC approach in the following paper to plates with complex support conditions, which have not been fully addressed in the literature yet.

Abstract-This letter introduces generalizations of the Perona-Malik equation. An edge enhancing functional is proposed for direct edge enhancement. A number of super diffusion operators is introduced for fast and effective smoothing. Statistical information is utilized for robust edge-stopping. Numerical integration is conducted by using a recently developed quasiinterpolating wavelet method. Computer experiments indicate that the present algorithm is very efficient for edge-detecting and noise-removing.