Cluster structure of <Superscript>16</Superscript>O

A folding potential describing the -scattering on ¹⁶O over a broad energy range 25.8-146.0 MeV is constructed on the basis of -like cluster and unclustered-nucleon configurations of ¹⁶O. The resulting potential does not need any renormalization to fit the angular distribution of elastic cross-sections. The effects of the repulsive part of - and -nucleon interactions are investigated. The analysis suggests that both the - repulsive potential and the unclustered nucleonic configuration in the target are important to describe the scattering data over a broad range of incident energies. The root-mean-square radius for the ¹⁶O nucleus is deduced.Received: 5 December 2002, Published online: 9 October 2003PACS: 25.55.Ci Elastic and inelastic scattering - 24.10.Ht Optical and diffraction models - 21.60.Gx Cluster models     

Characteristic features of Shannon information entropy of confined atoms

The Shannon information entropy of 1-normalized electron density in position and momentum space Sr and Sp, and the sum ST, respectively, are reported for the ground-state H, He+, Li2+, H-, He, Li+, Li, and B atoms confined inside an impenetrable spherical boundary defined by radius R. We find new characteristic features in ST denoted by well-defined minimum and maximum as a function of confinement. The results are analyzed in the background of the irreducible lower bound stipulated by the entropy uncertainty principle [I. Bialynicki-Birula and J. Mycielski, Commun. Math. Phys. 44, 129 (1975)]. The spherical confinement model leads to the ST values which satisfy the lower bound up to the limits of extreme confinements with the interesting new result displaying regions over which a set of upper and lower bounds to the information entropy sum can be locally prescribed. Similar calculations on the H atom in 2s excited states are presented and their novel characteristics are discussed.     

L^p（R^n） Boundedness for the Maximal Operator of Multilinear Singular Integrals with Calderon-Zygmund Kernels

In this paper, the authors consider a class of maximal multilinear singular integral operators and maximal multilinear oscillatory singular integral operators with standard Calderón–Zygmund kernels, and obtain their boundedness on L ^p (ℝ ⁿ ) for 1 < p < ∞. Research supported by Professor Xu Yuesheng’s Research Grant in the program of "One hundred Distinguished Young Scientists" of the Chinese Academy of Sciences     

Spatial unmasking of birdsong in human listeners: energetic and informational factors

Spatial unmasking describes the improvement in the detection or identification of a target sound afforded by separating it spatially from simultaneous masking sounds. This effect has been studied extensively for speech intelligibility in the presence of interfering sounds. In the current study, listeners identified zebra finch song, which shares many acoustic properties with speech but lacks semantic and linguistic content. Three maskers with the same long-term spectral content but different short-term statistics were used: (1) chorus (combinations of unfamiliar zebra finch songs), (2) song-shaped noise (broadband noise with the average spectrum of chorus), and (3) chorus-modulated noise (song-shaped noise multiplied by the broadband envelope from a chorus masker). The amount of masking and spatial unmasking depended on the masker and there was evidence of release from both energetic and informational masking. Spatial unmasking was greatest for the statistically similar chorus masker. For the two noise maskers, there was less spatial unmasking and it was wholly accounted for by the relative target and masker levels at the acoustically better ear. The results share many features with analogous results using speech targets, suggesting that spatial separation aids in the segregation of complex natural sounds through mechanisms that are not specific to speech.     

Electron correlation and fermi surface topology of NaxCoO2

The electronic structure of NaxCoO2 revealed by recent photoemission experiments shows important deviations from band theory predictions. The six small Fermi surface pockets predicted by local-density approximation calculations have not been observed as the associated e'(g) band fails to cross the Fermi level for a wide range of sodium doping concentration x. In addition, significant bandwidth renormalizations of the t(2g) complex have been observed. We show that these discrepancies are due to strong electronic correlations by studying the multiorbital Hubbard model in the Hartree-Fock and strong-coupling Gutzwiller approximation. The quasiparticle dispersion and the Fermi surface topology obtained in the presence of strong local Coulomb repulsion are in good agreement with experiments.     

A high-resolution 19F NMR spectroscopic study of barium fluorozirconate glasses and related crystals

Fluorozirconate glasses have attracted considerable attention not only for their transparency in the infrared, but also due to their high fluorine ion conductivities and extreme fragility in the viscosity-temperature relationship. We report on structural studies of binary BaF2-ZrF4 glasses with 58-78 mol% ZrF4 using high-resolution magic-angle-spinning 19F NMR. High-speed 19F MAS NMR allows us to resolve at least three unique fluorine environments in these binary glasses. These fluorine environments are attributed to one type of bridging fluorine, between corner-sharing Zr-F coordination polyhedra, and two types of non-bridging fluorine (NBF), one of which is bonded to one Zr and one Ba atom while the other is bonded to one Zr and two Ba atoms. The concentration of the first type of NBF increases with decreasing ZrF4 concentration, while that of the second type is essentially independent of glass composition. These assignments have been made on the basis of detailed 19F NMR studies of a wide variety of crystalline fluorozirconates with known crystal structures. A comparison between the glass and crystal 19F NMR spectra rules out any significant concentration of edge-shared Zr-F polyhedra in these binary glasses. The Zr atoms in all glasses are found to be coordinated to approximately 7.8+/-0.2F atoms.     

On the decaying states and the transition rates

The object of this paper is to point out that the hypothesis of decaying states,i.e., states with amplitude having a factor e^γt (γ-real) is not compatible with the wave equation with a hermitian hamiltonian. An attempt has been made to obtain the expression for relative population density in general. It is shown that the usual expressions for the transition rates, which are proportional to time, may be obtained for a very restricted interval of time.     

Alkaline degradation of tetraazahomoadamantane derivatives

Alkaline degradation of 1,3-6,8-tetraazatricyclo [4,4,1,1^3,8)dodecane (V) and 11-Thia-1,3,5,7-tetraazatricyclo[3,3,1,1^3,7 ]undecane-11,11-dioxide (VIII) are shown to generate readily formaldehyde and the respective amines, followed by resynthesis of imidazolidines in the presence of acylating or sulfonylating agents.     

An investigation into the electro-oxidation of ethanol and 2-propanol for application in direct alcohol fuel cells (DAFCs)

A comparative study of the electro-oxidation of ethanol and 2-propanol was carried out on carbon-supported platinum particles. Cyclic voltammetry, steady state polarisation, and electrochemical impedance spectroscopy were used to investigate the oxidation reactions. A difference in the mechanistic behaviour of the oxidation of ethanol and 2-propanol on Pt was observed, thereby highlighting the fact that the molecular structure of the alcohol has great influence on its electroreactivity. The study emphasizes the fact that 2-propanol is a promising fuel candidate for a direct alcohol fuel cell.