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排序方式: 共有2576条查询结果,搜索用时 15 毫秒
1.
Yimei Wang Yi Qiao Xiaomin Xu Xiaohong Ding Weiwei Li Bo Yuan Haiyan Xu 《Biomedical chromatography : BMC》2019,33(8)
A sensitive and reliable LC–MS/MS method was developed and validated for simultaneous quantification of the major components of Huangqi–Honghua extact in rat plasma, including hydroxysafflor yellow A (HSYA), astragaloside IV (ASIV), calycosin‐7‐O‐β‐d ‐glucoside (CAG), calycosin, calycosin‐3′‐O‐glucuronide (C‐3′‐G) and calycosin‐3′‐O‐sulfate (C‐3′‐S). After extraction by protein precipitation with acetonitrile and methanol from plasma, the analytes were separated on a Hypersil BDS C18 column by gradient elution with acetonitrile and 5 mM ammonium acetate. The detection was carried out on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization source switched between negative and positive modes. HSYA was monitored in negative ionization mode from 0 to 4.9 min, and ASIV, CAG, calycosin, C‐3′‐G and C‐3′‐S were determined in positive ionization mode from 4.9 to 10 min. The lower limits of quantification of the analytes were 6.25 ng/mL for HSYA, 0.781 ng/mL for CAG and 1.56 ng/mL for ASIV and calycosin. The intra‐ and inter‐assay precision (RSD) values were within 13.43%, and accuracy (RE) ranged from ?8.75 to 9.92%. The validated method was then applied to the pharmacokinetic study of HSYA, ASIV, CAG, calycosin, C‐3′‐G and C‐3′‐S in rat after an oral administration of Huangqi–Honghua extract. 相似文献
2.
Two novel 2′-hydroxychalcone derivatives (i.e., M1 and M2) are explored in this work. We mainly focus on investigating the effects of photoexcitation on hydrogen bonds and on the excited-state intramolecular proton transfer (ESIPT) process. On the basis of calculations of electrostatic potential surface and intramolecular interactions, we verify the formation of hydrogen bond O1 H2···O3 in both S0 and S1 states. Exploring the ultraviolet–visible spectra in the liquid phase, our simulated results reappear in the experimental phenomenon. Analyzing molecular geometry and infrared stretching vibrational spectra, we confirm O1 H2···O3 is strengthened for both M1 and M2 in the S1 state. We further confirm that charge redistribution facilitates ESIPT tendency. Constructing potential energy curves, we find the ultrafast ESIPT behavior for M1, which is because of the deficiency of side hydroxyl moiety comparing with M2. This work makes a reasonable affiliation of the ESIPT mechanism for M1 and M2. We wish this paper could facilitate understanding these two novel systems and promote their applications. 相似文献
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Hu Haiyan 《Acta Mechanica Solida Sinica》1994,7(2):137-150
This paper deals with the numerical solution of high dimensional dynamic systems with nonsmooth characteristics, such as structural elastoplasticity, mechanical clearance and dry friction. As a stable periodic response of the system attracts its transient response, it may be extracted from the transient response somehow. The paper suggests a novel iteration scheme to extrapolate the periodic response from a short time history of its transient response by curve fitting. Compared with the current schemes such as shooting and incremental harmonic balancing, the present scheme makes full use of the information within the transient response and the system characters, then its computation efficiency has increased by an order and the numerical convergence depending on the initial iteration has greatly improved.The subject supported by the Chinese Foundation of Aeronautical Science 相似文献
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中性载体阳离子电极膜电化学的计算机数字模拟 总被引:1,自引:0,他引:1
对中性载体阳离子电极膜3种可能的传输模式进行了数字模拟,研究了淌度、浓度、配合物稳定常数以及阴离子亲脂性对电极电位响应的影响。模拟结果对于廓清这类电极响应机理,解释有关实验现象及指导新电极设计提供了有用的信息。 相似文献
7.
将酞菁锰(MnPc)掺入阳离子表面活性剂双十二烷基二甲基溴化铵(DDAB)的氯仿溶液,并涂布于热解石墨电极表面,待氯仿挥发后即制得MnPc-DDAB薄膜电极。循环伏安实验表明,在KBr溶液中,该薄膜电极有两对还原氧化峰,第一对峰的Epc1=-0.27V,Epa1=0.01V;第二对峰的Epc2=-0.76V,Epa2=-0.62V(vs.SCE)。本文着重探讨了第二对峰的电化学行为,估计了该体系的电荷传递扩散系数Dct和表观非均相电极反应速率常数K0′等电化学参数,并可将该薄膜电极用于催化三氯乙酸的电化学还原。 相似文献
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The magneto-structural correlation between a Mn(ll) ion, coordinated in an octahedral environment, and two nitronyl nitroxide
radical ligands in trans- and cis-metal-radical complexes is investigated by the broken symmetry (BS) approach within density functional theory (DFT).
The dependences of coupling constants J on three structural parameters: (i) bond angle θ (Mn-O-N (nitroxide)); (ii) rotating angle ψ, defined by the nitronyl nitroxide radical plane rotating around the axial Mn-O (nitroxide); (iii) bond distance R (Mn-O (nitroxide)) are directly calculated. Our calculations showed that both trans- and cis-Mn(ll)-radical complexes behave a stronger antiferromagnetic interaction, consistent with experiments. In view of
molecular orbital theory, the direct exchanges, including σ-type and π-type exchanges, are responsible for the magnetic exchange
pathways. There is a preferable linear correlation between the calculated coupling constants J and the overlap integral squares S b between the local magnetic orbitals at the various rotating angle ψ at the fixed bond angle θ and bond distance R, in both trans- and cis-Mn(ll)-radical complexes. 相似文献
10.
0IntroductionThe solid-state chemistry of manganese!car-boxylate coordination polymers has received growingattention over the past few years,owing to their fasci-nating network topologies and potential application inthe field of molecular magnetism and bi… 相似文献