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21.
Shougo Higashi 《Surface science》2006,600(3):591-597
We have studied the individual adsorption of Mn and Bi, and their coadsorption on Cu(0 0 1) by low-energy electron diffraction (LEED). For Mn, we have determined the c(2 × 2) structure formed at 300 K, whose structure had been determined by several methods. We reconfirmed by a tensor LEED analysis that it is a substitutional structure and that a previously reported large corrugation (0.30 Å) between substitutional Mn and remaining surface Cu atoms coincides perfectly with the present value. In the individual adsorption of Bi, we have found a c(4 × 2) structure, which is formed by cooling below ∼250 K a surface prepared by Bi deposition of ∼0.25 ML coverage at 300 K where streaky half-order LEED spots appear. The c(4 × 2) structure has been determined by the tensor LEED analysis at 130 K and it is a substitutional structure. In the coadsorption, we found a c(6 × 4) structure, which has been determined by the tensor LEED analysis. It is very similar to the previously determined structure of the c(6 × 4) formed by coadsorption of Mg and Bi, and embedded MnBi4 clusters are arranged in the top Cu layer instead of MgBi4. Large lateral displacements of Bi atoms in the c(6 × 4)-(Mn + Bi) suggest that the Mn atoms undergo the size-enhancement caused by their large magnetic moment. 相似文献
22.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
23.
A Volterra type integral equation in a Hilbert space with an additional linear operator L and a spectral parameter depending
on time is considered. If the parameter does not belong to the spectrum of L unconditional solvability of the considered problem
is proved. In the case where the initial value of the parameter coincides with some isolated point of the spectrum of the
operator L sufficient conditions for solvability are established. The obtained results are applied to the partial integral
equations associated with a contact problem of the theory of elasticity. 相似文献
24.
Saida Sultanic 《Integral Equations and Operator Theory》2006,55(4):573-595
The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman
space La2. We also analyze the analogous problem for weighted Bergman spaces La,α2, − 1 < α < ∞. 相似文献
25.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
26.
Nikolaos V. Tsekos Michael Garwood Kmil Ugurbil 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):187
A new technique is presented for generating myocardial tagging using the signal intensity minima of the transition zones between the bands of 0° and 360° rotations, induced by a tandem of two adiabatic delays alternating with nutations for tailored excitation (DANTE) inversion sequences. With this approach, the underlying matrix corresponds to magnetization that has experienced 0° or 360° rotations. The DANTE sequences were implemented from adiabatic parent pulses for insensitivity of the underlying matrix to B1 inhomogeneity. The performance of the proposed tagging technique is demonstrated theoretically with computer simulations and experimentally on phantom and on the canine heart, using a surface coil for both RF transmission and signal reception. The simulations and the experimental data demonstrated uniform grid contrast and sharp tagging profiles over a twofold variation of the B1 field magnitude. 相似文献
27.
Michel Hébert 《Archive for Mathematical Logic》1991,31(2):133-143
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform. 相似文献
28.
meso-Tetra(n-hexyloxycarbonyl)porphyrin was found to be converted into porphine, the mother compound of porphyrins, in a 77% yield when heated in aqueous sulfuric acid at 180 °C over 30 min under an inert atmosphere. The observation demonstrates that the substituted porphyrin serves as a novel and useful precursor for porphine. 相似文献
29.
We obtain upper bounds for the tail distribution of the first nonnegative sum of a random walk and for the moments of the overshoot over an arbitrary nonnegative level if the expectation of jumps is positive and close to zero. In addition, we find an estimate for the expectation of the first ladder epoch. 相似文献
30.