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1.
Dmitri V Sevenard Vyacheslav Ya SosnovskikhAlexander A Kolomeitsev Martin H KönigsmannGerd-Volker Röschenthaler 《Tetrahedron letters》2003,44(41):7623-7627
In a convenient and efficient procedure, the nucleophilic 1,4-trifluoromethylation of several α,β-enones using (trifluoromethyl)trimethylsilane was achieved. The high regioselectivity of the reaction has been reached by blocking the carbonyl moiety of the electrophile with a bulky aluminum-centered Lewis acid. 相似文献
2.
V. I. Pogorelov 《Radiophysics and Quantum Electronics》1995,38(7):417-422
A general expression describing the coherent scattering indicatrix by arbitrary inhomogeneities of the medium is derived. It is shown that a universal program can be devised for calculation of such indicatrices to avoid difficulties in the analytical and experimental investigations of the media through the wave processes.Institute of Applied Geophysics, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 631–638, July, 1995. 相似文献
3.
Nikolaií N. Nekhoroshev Dmitrií A. Sadovskií Boris I. Zhilinskií 《Annales Henri Poincare》2006,7(6):1099-1211
We introduce fractional monodromy in order to characterize certain non-isolated critical values of the energy–momentum map
of integrable Hamiltonian dynamical systems represented by nonlinear resonant two-dimensional oscillators. We give the formal
mathematical definition of fractional monodromy, which is a generalization of the definition of monodromy used by other authors
before. We prove that the 1:( − 2) resonant oscillator system has monodromy matrix with half-integer coefficients and discuss
manifestations of this monodromy in quantum systems.
Communicated by Eduard Zehnder
Submitted: February 25, 2005; Accepted: November 17, 2005 相似文献
4.
Numerical methods for the efficient integration of both stiff and nonstiff equations of motion of multibody systems having
the form of differential-algebraic equations (DAE) of index 3 are discussed. Linear multi-step ABM and BDF methods are considered
for the non-iterational integration of nonstiff DAE. The Park method is proposed for integration of stiff equations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Zhi C Bando Y Tang C Xie R Sekiguchi T Golberg D 《Journal of the American Chemical Society》2005,127(46):15996-15997
We report for the first time that boron nitride nanotubes (BNNTs) may be dissolved in organic solvents by wrapping them with a polymer. Transmission electron microscopy and cathodoluminescence studies indicate the strong pi-pi interactions between BNNTs and the polymer. A band gap ranging from 5.2 to 5.5 eV was documented for the BNNTs independent of their geometrical characteristics by using ultraviolet-visible absorption experiments on composite films and thin BNNT films prepared from solutions. 相似文献
6.
Talapin DV Shevchenko EV Murray CB Kornowski A Förster S Weller H 《Journal of the American Chemical Society》2004,126(40):12984-12988
We demonstrate the self-organization of CdSe nanorods into nematic, smectic, and crystalline solids. Layered colloidal crystals of CdSe nanorods grow by slow destabilization of a nanocrystal solution upon allowing the diffusion of a nonsolvent into the colloidal solution of nanocrystals. The colloidal crystals of nanorods show characteristic birefringence, which we assign to specific spherulite-like texture of each nanorod assembly. To demonstrate the general character of nanorod self-assembly technique, CdSe/CdS heterostructure nanorods were organized into highly luminescent superlattices. 相似文献
7.
Insulating tubular BN sheathing on semiconducting nanowires 总被引:1,自引:0,他引:1
Zhu YC Bando Y Xue DF Xu FF Golberg D 《Journal of the American Chemical Society》2003,125(47):14226-14227
An effective method was developed for generation of insulating tubular boron nitride (BN)-sheathed nanostructures. ZnS nanowires and multilayered Si-SiO2 nanowires were successfully sheathed with insulating tubular BN-forming nanocables. Both the semiconductor nanowire cores and the BN sheaths are crystalline with well-uniform morphologies. 相似文献
8.
The syntheses of 3,4- and 4,5-diiodophthalonitriles are described. Coupling of the latter compound with Pd(PPh(3))(2)Cl(2) and 1-octyne, 1-heptyne, 1-hexyne, 1-pentyne, and 3,3-dimethyl-1-butyne gave a series of 4,5-dialkynylphthalonitriles. Hydrogenation of 4,5-bis(1-pentynyl)phthalonitrile and 4,5-bis(3,3-dimethyl-1-butynyl)phthalonitrile gave 4,5-dipentylphthalonitrile and 4,5-bis(3,3-dimethylbutyl)phthalonitriles. Condensation of the dialkynylphthalonitriles with lithium 1-pentoxide in 1-pentanol gave 2,3,9,10,16,17,23,24-octaalkynylphthalocyanines, while intervention of the intermediate dilithium phthalocyanines with zinc acetate gave the related zinc(II) phthalocyanines. (1)H NMR spectroscopy of these octaalkynylphthalocyanines exhibited large chemical shifts (1-2 ppm) of the internal and aromatic protons at concentrations ranging from 10(-)(2) to 10(-)(5) M and at temperatures from 27 to 147 degrees C. The effects of aggregation phenomena are discussed. The importance of reporting concentration and temperature values for NMR spectra of phthalocyanines is stressed. 相似文献
9.
Catalyzed collapse and enhanced hydrogen storage of BN nanotubes 总被引:1,自引:0,他引:1
Tang C Bando Y Ding X Qi S Golberg D 《Journal of the American Chemical Society》2002,124(49):14550-14551
The novel morphology of BN nanotubes with a collapsed structure has been discovered by a metal-catalyzed treatment. The collapse causes the dramatic enlargement of a specific surface area of BN nanotubes and remarkably enhances the hydrogen storage capacity of BN nanotubes. 相似文献
10.
Protein-ligand interactions may lead to the formation of multiple molecular complexes in dynamic exchange, affecting the kinetic and thermodynamic characteristics of the binding equilibrium. We followed the dissociation kinetics of the transient and specific complex of an antithrombotic peptide N-acetyl-Asp(55)-Phe-Glu-Glu-Ile-Pro(60)-Glu-Glu-Tyr-Leu-Gln(65) with human prothrombin by use of (15)N NMR relaxation dispersion spectroscopy of the peptide. Every one of the five (15)N-labeled adjacent residues of the peptide exhibited apparently different kinetic exchange and relaxation behaviors, which were especially evident at different concentrations of prothrombin. Binding-induced (15)N relaxation dispersion of residues Phe(56), Glu(57), Glu(58), and Ile(59) can be fitted phenomenologically to a two-site on-and-off exchange mechanism with physically feasible relaxation and kinetic parameters obtained for residues Phe(56), Glu(58), and Ile(59), independent of the prothrombin concentration. The apparent kinetic parameters of Glu(57) show some dependence on the concentration of prothrombin and the extracted transverse relaxation rate for Glu(57) in the bound state was severalfold higher than that expected for a protein-peptide complex with a size of approximately 72 kDa. In addition, the equilibrium population of the bound peptide obtained for Glu(57) was inconsistent with those for Phe(56), Glu(58), and Ile(59) and with the prothrombin/peptide ratios used in the experiments. These discrepancies can be explained by the presence of two conformations for the peptide-protein complex exchanging at a rate of approximately 100 s(-)(1). In all, our study shows that fast dissociation of protein-peptide complexes can be studied quantitatively using peptide (15)N NMR relaxation dispersion measurements without a precise knowledge of the peptide and protein concentrations. In addition, protein titration was found to improve the accuracy of quantitative analysis and may make it possible to determine the rate of conformational changes within the protein-peptide complex. 相似文献