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981.
A variety of 1,4-thiazines, thiazoles, 1,4-dithines and 2,2′-bithiazoles containing fused naphthoquinone and related rings have been prepared. The compounds include several novel chromophoric heterocyclic system and their visible absorption spectra are discussed. 相似文献
982.
983.
用常压MOCVD法在GaAs衬底上生长了Zn1-xCdxSe-ZnSe多层结构.通过X-射线衍射谱和光致发光等方法判断,表明该材料为多量子阱结构.从室温下的透射光谱上可以观察到这种多量子阱中的n=1的激子吸收峰,并观测到起因子激子的ns量级的光学双稳态. 相似文献
984.
Liao LA Zhang F Dmitrenko O Bach RD Fox JM 《Journal of the American Chemical Society》2004,126(14):4490-4491
A new type of parallel kinetic resolution (PKR) is reported in which quasienantiomers with very similar reactivities give products whose chromatographic properties diverge upon the addition of fluoride. This concept of a reactivity/affinity switch is applied to the PKR of cyclopropene carboxylic acids with all-carbon quaternary centers. This is the first application of alpha-amino acid quasienantiomers in PKR, and it is a complementary approach for acyltransfer systems where the asymmetry is induced by the nucleophile rather than the leaving group. Excellent diastereoselectivities (ranging from 90:10 to 99.5:5) and good yields were obtained for both quasienantiomeric products, and the reactions can be run on significant scale because the separation is trivial. High-level DFT calculations (B3LYP functional with the 6-31+G(d,p) basis set) provided transition-state structures with relative energies that are in accord with the experimental observations. 相似文献
985.
986.
MENG Fanbo CHEN Bo LIU Guang DING Jianying & MA Hui . Department of Physics Key Laboratory of Atomic Molecular Nano Sciences Ministry of Educa- tion Tsinghua University Beijing China . Graduate School at Shenzhen Tsinghua University Shenzhen China 《中国科学G辑(英文版)》2005,48(3):336-344
Fluorescence fluctuation spectroscopy (FFS)[1,2] is a kind of fluorescence detection techniques suitable for monitoring interaction and transportation processes in a small detection zone of biological systems. FFS detects and analyzes the fluorescence signal of the fluorescent molecules in the detection zone to retrieve the dynamical parameters of the system including concentration, diffusion coefficient and interaction constants. FFS utilizes various statistical methods to analyze the data,… 相似文献
987.
We report the observation of enhanced near-infrared transmission through arrays of subwavelength coaxial metallic structures compared with that through comparable diameter hole arrays as a result of localized electromagnetic modes supported by the complex coaxial unit cell. Polarization and angle-dependent transmission measurements clearly demonstrate the coupling between this localized mode and delocalized surface plasmon modes. A generalized, multiple discrete states Fano line shape provides a good fit to the experimental results. 相似文献
988.
We report the integration of inorganic nanotubes into metal-oxide-solution field effect transistors (FETs) which exhibit rapid field effect modulation of ionic conductance. Surface functionalization, analogous to doping in semiconductors, can switch the nanofluidic transistors from p-type to ambipolar and n-type field effect transistors. Transient study reveals the kinetics of field effect modulation is controlled by ion-exchange step. Nanofluidic FETs have potential implications in subfemtoliter analytical technology and large-scale nanofluidic integration. 相似文献
989.
The effects of repeating thickness periods on stress are studied in ZrO2/SiO2 multilayers deposited by electron-beam evaporation on BK7 glass and fused-silica substrates. The results show that the residual stress is compressive and decreases with an increase of the periods of repeating thickness in the ZrO2/SiO2 multilayers. At the same time, the residual stress in multilayers deposited on BK7 glass is less than that of samples deposited on fused silica. The variation of the microstructure examined by x-ray diffraction shows that microscopic deformation does not correspond to macroscopic stress, which may be due to variation of the interface stress. 相似文献
990.
Distinguishability and indistinguishability by local operations and classical communication 总被引:1,自引:0,他引:1
Fan H 《Physical review letters》2004,92(17):177905
It is well known that orthogonal quantum states can be distinguished perfectly. However, if we assume that these orthogonal quantum states are shared by spatially separated parties, the distinguishability of these shared quantum states may be completely different. We show that a set of linearly independent quantum states [formula: see text] where U(m,n) are generalized Pauli matrices, cannot be discriminated deterministically or probabilistically by local operations and classical communication. On the other hand, any l maximally entangled states from this set are locally distinguishable if l(l-1)< or =2d. The explicit projecting measurements are obtained to locally discriminate these states. As an example, we show that four Werner states are locally indistinguishable. 相似文献