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Liang B Andrews L Li J Bursten BE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(19):4781-4788
Laser-ablated U atoms co-deposited with CO in excess neon produce the novel CUO molecule, which forms distinct Ng complexes (Ng=Ar, Kr, Xe) with the heavier noble gases. The CUO(Ng) complexes are identified through CO isotopic and Ng reagent substitution and comparison to results of DFT frequency calculations. The U[bond]C and U[bond]O stretching frequencies of CUO(Ng) complexes are slightly red-shifted from neon matrix (1)Sigma(+) CUO values, which indicates a (1)A' ground state for the CUO(Ng) complexes. The CUO(Ng)(2) complexes in excess neon are likewise singlet molecules. However, the CUO(Ng)(3) and CUO(Ng)(4) complexes exhibit very different stretching frequencies and isotopic behaviors that are similar to those of CUO(Ar)(n) in a pure argon matrix, which has a (3)A" ground state based on DFT vibrational frequency calculations. This work suggests a coordination sphere model in which CUO in solid neon is initially solvated by four or more Ne atoms. Up to four heavier Ng atoms successively displace the Ne atoms leading ultimately to CUO(Ng)(4) complexes. The major changes in the CUO stretching frequencies from CUO(Ng)(2) to CUO(Ng)(3) provides evidence for the crossover from a singlet ground state to a triplet ground state. 相似文献
114.
采用0.5μmpHEMT工艺研制了Gilbert式单片混频器,设计采用了电流注入技术及跨导级源端负反馈技术,在C波段测试表明:变频增益大于1.5dB,单边带噪声系数典型值为12.5dB,变频带宽约为DC~1GHz,所需本振功率实测值为1.6dBm。 相似文献
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Ngoc Vinh Huynh Thi Hoai Thu Nguyen Kim Phi Phung Nguyen Poul Erik Hansen 《Magnetic resonance in chemistry : MRC》2013,51(7):439-443
Tithonia tagetiflora Desv. (Asteraceae) is a widespread plant in Vietnam, and the species of Tithonia are known as plants containing many biologically active compounds. However, T. tagetiflora's chemical composition remains mostly unknown. Therefore, we now report the structural elucidation of two new sesquiterpene lactones, 8‐angeloyloxy‐2,14‐epoxygermacra‐4,10(1),11(13)‐trien‐6,12‐olide (1) and 6‐angeloyloxy‐1‐hydroxy‐3,4‐epoxygermacra‐9,11(13)‐dien‐8,12‐olide (2), together with three known compounds, including two norisoprenoids, (6S,9S)‐vomifoliol or (6R,9R)‐vomifoliol (3) and (6S,9S)‐roseoside (4), and one glutinane type triterpene, epi‐glutinol (5), from the leaves of T. tagetiflora. Their structures are established by 1D and 2D NMR spectroscopy, as well as ESI‐MS analysis and comparison with literature data. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Ting Hu Peng Wu Jianfeng Zhan Weixin Wang Junfeng Shen Chi-Tang Ho Shiming Li 《Molecules (Basel, Switzerland)》2021,26(11)
Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity. 相似文献
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A combination of two conventional junction isolation structures is used to produce a device, which significantly improves the blocking of minority carriers injected into the substrate of a power IC due to switching of an inductive load. Simulation results show that the connection scheme employed greatly enhances the efficiency of the structures. A substrate current reduction of up to four orders of magnitude compared to conventional junction isolation structures is achieved. The significance of doping profiles in the p-sinker region is evaluated. 相似文献
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氧化物隔离等平面S(z)工艺采用全离子注入工艺代替原始的扩散工艺,使得整个工艺流程更为简化,对于浅结工艺的重复性和均匀性均有较大提高。发射极条和基极条形成自对准,发射极四周靠墙。发射极条宽为3微米时,f_γ>3GHz。该工艺已应用于超高速双极ECL分频器中。 相似文献
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