Atomic structure of Al55(Cr1−xMnx)15Si30 metallic glasses observed by neutron diffraction

An atomic structure of Al₅₅(Cr_1−xMn_x)₁₅Si₃₀ (x = 0, 0.49,1) metallic glasses was studied by neutron diffraction. An advantage of the neutron diffraction technique was fully exploited by utilizing the negative scattering length of Mn to form a neutron zero scattering ‘alloy’ for the component Cr_0.51Mn_0.49 in this quaternary Al---(Cr, Mn)---Si alloy. This allows the atomic distribution of the resulting quasibinary Al---Si metallic glass to be derived directly. Moreover, the (Al, Si)---TM (TM = Mn, Cr) and TM---TM pair correlations were also extracted by taking appropriate linear combinations of the atomic structures for the Al₅₅(Cr_1−xMn_x)₁₅Si₃₀ (x = 0, 0.49, 1) metallic glasses. A sharp first peak in the (Al,Si) ---TM pair correlations thus obtained led to the conclusion that a strong attractive interaction exists between (Al, Si) and TM atoms and, hence, that the presence of the TM atoms is responsible for the formation of an amorphous phase.     

Role of heme propionates of myoglobin in vibrational energy relaxation

The role of heme propionates of myoglobin in vibrational energy relaxation was studied by time-resolved resonance Raman spectroscopy. Time-resolved anti-Stokes spectra were measured to monitor the vibrational energy relaxation of the heme. The decay rates of the band intensities were compared between wild-type myoglobin and etioheme-substituted myoglobin where the heme lacks hydrogen-bonding side chains. The decay rates of the anti-Stokes intensities of the latter were less than those of the former, providing strong support for a theoretical proposal that the propionates and their coupling to solvent bath play an important role in the dissipation of excess energy of the excited heme in solvated wild-type myoglobin.     

Electronic properties of Gd@C<Subscript>82</Subscript> metallofullerene peapods: (Gd@C<Subscript>82</Subscript>)<Subscript>n</Subscript>@SWNTs

Electronic properties of Gd@C₈₂ metallofullerene peapods, (Gd@C₈₂)_n@SWNTs, were investigated by electron energy-loss spectroscopy (EELS), scanning tunneling microscopy and spectroscopy (STM/STS), and field-effect transistor (FET) transport measurements. The results indicate that the electronic structure of Gd@C₈₂ metallofullerene peapods is completely different from that of intact single-walled nanotubes (SWNTs). For example, Gd@C₈₂-peapod-FETs show ambipolar behavior which is not observed in the empty SWNT-FETs under our experimental conditions. Furthermore, in semiconducting nanotubes the band gap can be varied from ∼0.5 to ∼0.1 eV using inserted Gd@C₈₂ endohedral metallofullerenes with a spatial periodicity of 1.1 to 8.0 nm, depending on the density of the fullerenes. The present findings suggest that metallofullerene peapods may point the way toward novel electronic devices. Received: 6 September 2002 / Accepted: 25 October 2002 / Published online: 10 March 2003 RID="*" ID="*"Corresponding author. Fax: +81-52/789-1169, E-mail: noris@cc.nagoya-u.ac.jp     

Characterization of defect type and dislocation density in double oxide heteroepitaxial CeO2/YSZ/Si(001) films

In order to qualitatively and quantitatively analyze the structural defects including the defect types and their concentrations in oxide heteroepitaxial films, a new X-ray rocking-curve width-fitting method was used in the case of doubleCeO₂/YSZ/Si (YSZ=yttria-stabilized ZrO₂) films that were prepared by pulsed laser deposition. Two main defect types, angular rotation and oriented curvature, were found in both CeO₂ and YSZ. Dislocation densities of CeO₂ and YSZ, which were obtained from the angular rotations, are functions of the YSZ thickness. A distinct two-step correlation between dislocation densities of CeO₂ and YSZ was found that as the dislocation density of YSZ is higher than 2.4×10¹¹ cm^-2, the dislocation density of CeO₂ shows a high sensitivity with that of YSZ compared with the low relativity in lower dislocation density (<2.4×10¹¹ cm^-2). In addition, YSZ always has higher dislocation densities and oriented curvatures than CeO₂ in each specimen, which can be attributed to the smaller mosaic domain sizes in YSZ than in CeO₂ as observed by high-resolution transmission electron microscopy. Received: 12 August 2002 / Accepted: 14 August 2002 / Published online: 4 December 2002 RID="*" ID="*"Corresponding author. Fax: +81-3/5734-3369, E-mail: chun_hua_chen@hotmail.com     

A.C; A′.C′-doubly capped δ-cyclodextrin. Direct evidence for the capping structure

Doubly capped β-cyclodextrin was firstly prepared in good yield by the treatment of β- cyclodextrin with an excess amount (2.6/1 mol/mol) of benzophenone-3,3′-disulfonyl chloride. This successful double capping demonstrates that benzophenone-3,3′-disulfonyl capping takes place on A,C rings. The present double cap is a useful key intermediate for the preparation of regiospecifically tetrasubstituted cyclodextrins.