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991.
992.
The interaction of cobalt atoms with silicon (1 1 1) surface has been investigated by means of scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Besides the Co silicide islands, we have successfully distinguished two inequivalent Co-induced reconstructions on Si(1 1 1) surface. Our high-resolution STM images provide some structural properties of the two different derived phases. Both of the two phases seem to form islands with single domain. The new findings will help us to understand the early stage of Co silicide formations. 相似文献
993.
Y. Liu H. Shi J. Ma D. Gan J. Cui C. Du X. Luo 《Applied physics. B, Lasers and optics》2008,92(4):623-626
The authors theoretically demonstrate the terahertz beam shaping with metallic subwavelength holes array surrounded by concentric
periodic grooves. High transmission and directional radiation can be obtained simultaneously for the resonant excitation of
the surface wave in the combined structure. Finite-difference time-domain simulation results shows that the transmission mainly
depends on the lattice constant of hole array and the features of incident surface around it, while the far-field angle distribution
is dominated by the details of the output surface. This compact beam shaping structure is hoped to serve as a basic device
for future terahertz systems. 相似文献
994.
In this paper, some improvements on Darvishi and Hessari [On convergence of the generalized AOR method for linear systems with diagonally dominant coefficient matrices, Appl. Math. Comput. 176 (2006) 128–133] are presented for bounds of the spectral radius of lω,r, which is the iterative matrix of the generalized AOR (GAOR) method. Subsequently, some new sufficient conditions for convergence of GAOR method will be given, which improve some results of Darvishi and Hessari [On convergence of the generalized AOR method for linear systems with diagonally dominant coefficient matrices, Appl. Math. Comput. 176 (2006) 128–133]. 相似文献
995.
A general and concise synthesis of functionalized indoles via domino reaction of N-aryl amides and ethyl diazoacetate has been developed. The methodology offers a great potential for the synthesis of biologically active and naturally occurring indole derivatives. 相似文献
996.
Kissounko DA Hoerter JM Guzei IA Cui Q Gellman SH Stahl SS 《Journal of the American Chemical Society》2007,129(6):1776-1783
Titanium(IV)-mediated reactions between primary amines and secondary carboxamides exhibit different outcomes, amidine formation versus transamidation, depending on the identity of the TiIV complex used and the reaction conditions employed. The present study probes the origin of this divergent behavior. We find that stoichiometric TiIV, either Cp*TiIV complexes or Ti(NMe2)4, promotes formation of amidine and oxotitanium products. Under catalytic conditions, however, the outcome depends on the identity of the TiIV complex. Competitive amidine formation and transamidation are observed with Cp*TiIV complexes, generally favoring amidine formation. In contrast, the use of catalytic Ti(NMe2)4 (< or =20 mol %) results in highly selective transamidation. The ability of TiIV to avoid irreversible formation of oxotitanium products under the latter conditions has important implications for the use of TiIV in catalytic reactions. 相似文献
997.
998.
999.
Fang L Park JY Cui Y Alivisatos P Shcrier J Lee B Wang LW Salmeron M 《The Journal of chemical physics》2007,127(18):184704
The mechanical and electrical properties of CdTe tetrapod-shaped nanocrystals have been studied with atomic force microscopy. Tapping mode images of tetrapods deposited on silicon wafers revealed that they contact the surface with three of its arms. The length of these arms was found to be 130+/-10 nm. A large fraction of the tetrapods had a shortened vertical arm as a result of fracture during sample preparation. Fracture also occurs when the applied load is a few nanonewtons. Compression experiments with the atomic force microscope tip indicate that tetrapods with the shortened vertical arm deform elastically when the applied force was less than 50 nN. Above 90 nN additional fracture events occurred that further shortened the vertical arm. Loads above 130 nN produced irreversible damage to the other arms as well. Current-voltage characteristics of tetrapods deposited on gold revealed a semiconducting behavior with a current gap of approximately 2 eV at low loads (<50 nN) and a narrowing to about 1 eV at loads between 60 and 110 nN. Atomistic force field calculations of the deformation suggest that the ends of the tetrapod arms are stuck during compression so that the deformations are due to bending modes. Empirical pseudopotential calculation of the electron states indicates that the reduction of the current gap is due to electrostatic effects, rather than strain deformation effects inside the tetrapod. 相似文献
1000.
The synthesis of a novel class of 2-imino-5-arylidene-3-pyrrolines via a copper-catalyzed multicomponent reaction of sulfonyl azides with alkynes and aziridines is described. The protocol is efficient and general. 相似文献