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51.
应用密度泛函理论对杯[4]吡咯及卤素取代杯[4]吡咯模型分子的自由主体以及其卤素离子复合物体系进行计算研究. 结果表明, 杯[4]吡咯β位被卤素拉电子基团取代后, 主体分子的构象特征受吡咯单元的偶极影响; β-卤素取代导致了杯[4]吡咯对卤素离子的结合作用增强, 且当β位为氯取代时, 杯[4]吡咯对卤素离子的结合能力最强. 并从振动光谱、NBO电荷布居、相互作用的前线轨道、“活性”构象的偶极矩和Mulliken成键布居等方面阐述β-卤素取代对杯[4]吡咯与卤素离子之间的主-客体相互作用的影响. 相似文献
52.
53.
Spacer layer thickness fluctuation scattering in a modulation-doped AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well 下载免费PDF全文
We theoretically study the influence of spacer layer thickness fluctuation(SLTF) on the mobility of a twodimensional electron gas(2DEG) in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer. 相似文献
54.
Cheng-Ming Chu 《Tetrahedron letters》2007,48(39):6881-6885
Iodine mediates the hydroarylation of styrenes with arenes and heteroarenes to afford 1,1-diarylalkanes in good to high yields. Details regarding the substrate scope and selectivity of this hydroarylation reaction are discussed. 相似文献
55.
Po-Yen Tseng Huan-Chang Hsiao Cheng-Ming Hsieh An-Ju Wu Shih-Ching Chuang 《中国化学会会志》2020,67(3):430-436
Organic bulk heterojunction photovoltaics, merely incorporating monoadducts of cyclopenteno[60]fullerenes (CPFs) as n-type materials and P3HT as p-type materials, display superior power conversion efficiency up to 4.6 ± 0.12%, superseding that with PC61BM/P3HT (3.8 ± 0.20%) for ca. 20%, under AM 1.5G irradiation―primarily attributed to the lack of homo-conjugation on CPFs and their higher LUMO energy levels. 相似文献
56.
Based on polyethylene glycol modified single-walled carbon nanotubes, a novel sol–gel fiber coating was prepared and applied
to the headspace microextraction of chlorinated organic carriers (COCs) in textiles by gas chromatography-electron capture
detection. The preparation of polyethylene glycol modified single-walled carbon nanotubes and the sol–gel fiber coating process
was stated and confirmed by infrared spectra, Raman spectroscopy, and scanning electron microscopy. Several parameters affecting
headspace microextraction, including extraction temperature, extraction time, salting-out effect, and desorption time, were
optimized by detecting 11 COCs in simulative sweat samples. Compared with the commercial solid-phase microextraction fibers,
the sol–gel polyethylene glycol modified single-walled carbon nanotubes fiber showed higher extraction efficiency, better
thermal stability, and longer life span. The method detection limits for COCs were in the range from 0.02 to 7.5 ng L−1 (S/N = 3). The linearity of the developed method varied from 0.001 to 50 μg L−1 for all analytes, with coefficients of correlation greater than 0.974. The developed method was successfully applied to the
analysis of trace COCs in textiles, the recoveries of the analytes indicated that the developed method was considerably useful
for the determination of COCs in ecological textile samples. 相似文献
57.
The symmetry operator Q = Y2 is introduced to re-describe the Heisenberg spin triangles in the {V6} molecule, where Y stands for the Yangian operator which can be viewed as special form of Dzyaloshinsky–Moriya (DM) interaction for spin 1/2 systems. Suppose a parallelogram Heisenberg model that is comprised of four -spins commutes with Q, which mean that it possesses Yangian symmetry, we show that the ground state of the Hamiltonian H4 for the model allows to take the total spin S = 1 by choosing some suitable exchange constants in H4. In analogy to the molecule {V6} where the two triangles interact through Yangian operator we then give the magnetization for the theoretical molecule “{V8}” model which is comprised of two parallelograms. Following the example of molecule {V15}, we give another theoretical molecule model regarding the four -spins system with total spin S = 1 and predict the local moments to be , respectively. 相似文献
58.
Wu Fan Zhu Ya-Ning Hou Yu-Ting Mi Qi-Li Chen Jian-Hua Zhang Cheng-Ming Miao Dong Zhou Min Wang Wei-Guang Hu Qiu-Fen Ye Yan-Qing Li Xue-Mei 《Chemistry of Natural Compounds》2021,57(5):823-827
Chemistry of Natural Compounds - Two new anthraquinones, 3-hydroxy-6-hydroxymethyl-2,5-dimethylanthraquinone (1) and 6-hydroxymethyl-3-methoxy-2,5-dimethylanthraquinone (2), were isolated from the... 相似文献
59.
Cliuan Yue Peng-Xiong Ma Qiang Yuan Yi-Zhong Fan Zhan-Fang Chen Ming-Yang Cui Hao-Ting Dai Tie-Kuang Dong Xiaoyuan Huang Wei Jiang Shi-Jun Lei Xiang Li Cheng-Ming Liu Hao Liu Yang Liu Chuan-Ning Luo Xu Pan Wen-Xi Peng Rui Qiao Yi-Feng Wei Li-Bo Wu Zhi-Hui Xu Zun-Lei Xu Guan-Wen Yuan Jing-Jing Zang Ya-Peng Zhang Yong-Jie Zhang Yun-Long Zhang 《Frontiers of Physics》2020,15(2):24601-109,F0004
Precise measurements of the energy spectra of cosmic rays(CRs)show various kinds of features deviating from single power-laws,which give very interesting and important implications on their origin and propagation.Previous measurements from a few balloon and space experiments indicate the existence of spectral softenings around 10 TV for protons(and probably also for Helium nuclei).Very recently,the DArk Matter Particle Explorer(DAMPE)measurement about the proton spectrum clearly reveals such a softening with a high significance.Here we study the implications of these new measurements,as well as the groundbased indirect measurements,on the origin of CRs.We find that a single component of CRs fails to fit the spectral softening and the air shower experiment data simultaneously.In the framework of multiple components,we discuss two possible scenarios,the multiple source population scenario and the background plus nearby source scenario.Both scenarios give reasonable fits to the wide-band data from TeV to 100 PeV energies.Considering the anisotropy observations,the nearby source model is favored. 相似文献
60.
A new Digital Pulse Processing(DPP) module has been developed, based on a domino ring sampler version 4 chip(DRS4), with good time resolution for La Br3 detectors, and different digital timing analysis methods for processing the raw detector signals are reported. The module, composed of an eight channel DRS4 chip, was used as the readout electronics and acquisition system to process the output signals from XP20D0 photomultiplier tubes(PMTs). Two PMTs were coupled with La Br3 scintillators and placed on opposite sides of a radioactive positron22 Na source for 511 ke V γ-ray tests. By analyzing the raw data acquired by the module, the best coincidence timing resolution is about 194.7 ps(FWHM), obtained by the digital constant fraction discrimination(d CFD) method,which is better than other digital methods and analysis methods based on conventional analog systems which have been tested. The results indicate that it is a promising approach to better localize the positron annihilation in positron emission tomography(PET) with time of flight(TOF), as well as for scintillation timing measurement,such as in TOF-?E and TOF-E systems for particle identification, with picosecond accuracy timing measurement.Furthermore, this module is more simple and convenient than other systems. 相似文献