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41.
The relationship among the Wigner crystal, charge ordering, and the Mott insulator is studied by the path-integral renormalization group method in two-dimensional systems with long-range Coulomb interaction. In contrast to the insensitivity of the Hartree-Fock results, the stability of the solid drastically decreases with the decrease in the lattice commensurability. The transition to liquid occurs at the electron gas parameter r(s) approximately 2 for the filling n=1/2, showing a large reduction from r(s) approximately 35 in the continuum limit. A correct account of quantum fluctuations is crucial to understanding the charge-order stability generally observed only at simple fractional fillings and the nature of quantum liquids away from them. 相似文献
42.
Noda Susumu Imada Masahiro Chutinan Alongkarn Yamamoto Noritsugu 《Optical and Quantum Electronics》2002,34(8):723-736
Three-dimensional (3D) and two-dimensional (2D) photonic crystals based on III–V semiconductors are described. On the 3D photonic crystals, the development of complete photonic crystals at optical wavelengths and their applications to ultrasmall optical integrated circuits including 3D sharp bend waveguide are described. On the 2D photonic crystals, two-unique device and/or phenomena are demonstrated. 相似文献
43.
We investigate the hadron productions in hyperon proton collisions in terms of the quark-diquark cascade model with diffractive component. We compare our predicted spectra Ξ?→Ξ? X and Ξ?→Ω? X with the experimental data. The distribution functions of constituents in incident hadrons and the momentum sharing functions of cascade processes are characterized by the intercepts of Regge trajectories, revealing the difference betweens quark and non-strange quark. 相似文献
44.
The regioselective ring-opening reaction of α-methyl-β-propiolactone with 3,3-ethylene-dioxybutylmagnesium bromide in the presence of copper(I) catalyst afforded 2-methyl-6-oxoheptanoic acid, which was easily converted into (E)-3,7-dimethyl-2-2-octene-1,8-diol in good yield. 相似文献
45.
A new synthetic approach to quinazolines bearing a carboxy group is described. Reaction of 5-carbonyl substituted 1,3,6-tri-methyluracils (I) with dimethyl acetylenedicarboxylate or electron-deficient olefines affords quinazoline derivatives (III-VI) pyrimidine(Z)-dienols (II) formed by base-catalyzed isomerization. 相似文献
46.
47.
48.
The effect of disorder on the superconducting transition temperature T(c) of cuprate superconductors is examined. Disorder is introduced into the cation sites in the plane adjacent to the CuO2 planes of two single-layer systems, Bi(2.0)Sr(1.6)Ln(0.4)CuO(6+delta) and La(1.85-y)Nd(y)Sr0.15CuO4. Disorder is controlled by changing rare earth (Ln) ions with a different ionic radius in the former, and by varying the Nd content in the latter with the doped carrier density kept constant. We show that this type of disorder works as weak scatterers in contrast to the in-plane disorder produced by Zn, but remarkably reduces T(c), suggesting novel effects of disorder on high-T(c) superconductivity. 相似文献
49.
Q. Hu H. Araki H. Suzuki N. Ishikawa W. Yang T. Noda 《Applied Physics A: Materials Science & Processing》2003,76(4):561-563
A few of the interesting structures made by the assemblage of Si-Ge nanowires fabricated by the floating-zone melting-vapor
method have been observed. They reveal shapes that are similar to coral, jellyfish and sea anemones. The pre-sintered substrate
bar has some large crystalline particles (1–15 μm), which produce sites that are energetically predisposed to nucleation.
The peculiar structures created by the assemblage of Si-Ge nanowires form on favored nucleation sites that consist of numerous
bundles of nanowires with diameters of 20–50 nm. The periodic variation in the diameter of the bundles of nanowires is a common
feature of these structures. In addition, a growth mechanism assisted by the coexistence of Ge and Si-Ge oxides is suggested.
The growth process of these assemblages opens up new possibilities for the study of the growth mechanism of Si-Ge nanowires.
Received: 25 July 2002 / Accepted: 9 September 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: 81-298/59-2736, E-mail: HU.Quanli@nims.go.jp 相似文献
50.
Adamus G Sikorska W Kowalczuk M Noda I Satkowski MM 《Rapid communications in mass spectrometry : RCM》2003,17(20):2260-2266
We report an electrospray ionisation multistage mass spectrometry (ESI-MSn) method that utilises molecular mass information for determination of sequence distribution and chemical structure of mass-selected macromolecules of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) biopolyester, PHBH. On the basis of ESI-MSn studies of PHBH oligomers obtained by partial alkaline depolymerisation of natural PHBH containing 13-14 mol% of hydroxyhexanoate (HH) units, the microstructure of this bacterial copolyester was assessed up to the level of 28 repeat units. The subtle structural details of the PHBH were evaluated based on sequencing of individual macromolecular ions thus showing the utility of this technique for the analysis of biological copolyester macromolecules. It was confirmed that both HH and hydroxybutyrate (HB) units of the PHBH copolymer are randomly distributed. 相似文献