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991.
Zexi Liu Jing Ai Dr. Prashant Kumar Enming You Dr. Xiong Zhou Dr. Xi Liu Prof. Zhongqun Tian Prof. Petr Bouř Dr. Yingying Duan Prof. Lu Han Prof. Nicholas A. Kotov Prof. Songyuan Ding Prof. Shunai Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(35):15338-15343
A surface-enhanced Raman scattering-chiral anisotropy (SERS-ChA) effect is reported that combines chiral discrimination and surface Raman scattering enhancement on chiral nanostructured Au films (CNAFs) equipped in the normal Raman scattering Spectrometer. The CNAFs provided remarkably higher enhancement factors of Raman scattering (EFs) for particular enantiomers, and the SERS intensity was proportional to the enantiomeric excesses (ee) values. Except for molecules with mesomeric species, all of the tested enantiomers exhibited high SERS-ChA asymmetry factors (g), ranging between 1.34 and 1.99 regardless of polarities, sizes, chromophores, concentrations and ee. The effect might be attributed to selective resonance coupling between the induced electric and magnetic dipoles associated with enantiomers and chiral plasmonic modes of CNAFs. 相似文献
992.
M. An Q. Y. Chen B. Q. Ai P. Deng X. Q. Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(8):1-4
Contributions of homogeneous and Goldstone modes of the spin precession were distinguished in FMR spectra of Cr1/3NbS2 chiral helimagnet. The resonance field of homogeneous mode is determined by uniaxial magnetic anisotropy. The resonance field of Goldstone mode is determined by six-fold anisotropy in basal plane. For the first time, it has been shown experimentally that effective excitation of Goldstone mode is realized only when microwave magnetic field vector h is perpendicular to wave vector of magnetic structure Q. 相似文献
993.
The microstructures of a single-crystal nickel-base superalloy were observed by transmission electron microscopy (TEM) before and after thermo-mechanical fatigue. Both dislocation configurations and γ′ precipitate morphologies under in-phase (IP) testing were found to be clearly different from those under out-of-phase (OP) testing. Under IP testing, dense hexagonal dislocation networks were found on the horizontal interfaces, and irregular dislocation networks on the vertical interfaces. With decreasing mechanical strain amplitude, rafting of γ′ precipitates was more pronounced. Under OP testing, no dislocation networks were found on the γ/γ′ interfaces; also, γ′ precipitates were sheared by superlattice stacking faults, and were not clearly rafted. The characteristic dislocation networks and partials of the stacking fault are analysed and the rafting mechanism of the γ′ precipitates is discussed. 相似文献
994.
Itaru Sakurai Jinji Suzuki Yoshinobu Kotani Hiroyoshi Naito Akira Yoshida 《Proceedings of the Combustion Institute》2013,34(2):2727-2734
In the present study, extinguishment of propane/air co-flowing diffusion flame by fine water droplets was investigated experimentally. Water droplets are generated by piezoelectric atomizers with the maximum droplets flow rate of 1500 ml/h. When the fuel injection velocity Uf is low, an attached laminar diffusion flame with a premixed flame at the base is stabilized. At some distance from the burner rim, a transition from laminar to turbulent diffusion flame occurs, and a turbulent diffusion flame is formed in the downstream region. When the fuel injector rim is thin (δ = 0.5 mm), the flame stability deteriorates with increase of the co-flowing air stream velocity Ua and the water droplets flow rate Qm. The stability mechanism can be explained by the balance of the gas velocity and the burning velocity of premixed flame formed at the base. However, when the injector rim is thick (δ = 5 mm), a recirculation zone is produced downstream of the injector rim. The dependence of the quenching distance Hq on Uf and Qm is relatively weak, and the stability diagram shows curious features. It was shown that Ua is crucially important since it determines flow residence time; if Ua < 0.4 m/s, water droplets can evaporate when they go by the recirculation zone, and the water vapor can diffuse into the recirculation zone. However, if Ua > 0.4 m/s, the water droplets should pass by the recirculation zone without sufficiently evaporated and are not so effective to extinguish the flame. The supply velocity of droplet-laden air should be low enough so that water droplets can evaporate and water vapor can diffuse into the premixed region at the base to obtain sufficient effectiveness of water droplets for fire suppression. 相似文献
995.
996.
Two novel core-extended terrylene diimides on the bay region (CETDIs) were synthesized via annulation of the four additional ethylene units or benzene units on the bay region of the terrylene diimide core. The optical and electrochemical properties of the two compounds were investigated. These CETDIs exhibited broad absorption spectra with high extinction coefficients, which span a wide range in the ultraviolet and visible spectrum from 300 to 700 nm. Furthermore, the redox process of the CETDIs increased from two waves to four waves, and the lowest unoccupied molecular orbital (LUMO) levels were enhanced from -4.00 to -3.59 eV. 相似文献
997.
A highly efficient and convenient method for the synthesis of 1,2,4,5-tetrasubstituted imidazoles from readily accessible 2-azido acrylates and nitrones has been developed. This reaction proceeded under mild conditions without the assistance of any metal, acid, or base. 相似文献
998.
A new [X+2+Y]-type for the convergent synthesis of polycyclic ethers based on an oxiranyl anion strategy was developed. The sequence involves nucleophilic substitution of a triflate with an oxiranyl anion followed by 6-endo cyclization, ring expansion, and reductive etherification. The protocol features a flexible approach toward trans-fused polycyclic arrays consisting of six- and seven-membered ether rings from the same starting materials. 相似文献
999.
1000.
为实现二极管激光器垂直阵列输出光束具有小发散角、高指向精度的特点,简述了快轴准直(FAC)微透镜的光束准直原理,分析了调节装置的精度要求及透镜选择等问题。通过光学成像方法实时监测二极管激光bar条的近场像和远场像,对FAC透镜分别进行粗调节和细调节,获得了20个bar条连续输出2 kW,垂直阵列二极管激光快轴准直光束远场发散角4.4 mrad,bar条间准直光束指向精度不大于±1.7 mrad的准直效果,并对监测精度进行了简要分析。对影响光束准直效果的因素进行了分析,指出了工艺优化的重点。 相似文献