排序方式: 共有42条查询结果,搜索用时 0 毫秒
1.
Xu-Feng Tan Li-Yong Yuan Chang-Ming Nie Kui Lui Zhi-Fang Chai Wei-Qun Shi 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):281-288
Electrochemical behaviors of U(VI) in 1-butyl-3-methylimidazolium chloride (C4MimCl) with various water contents investigated by chronopotentiometry and cyclic voltammetry. The electrochemical reduction of U(VI) was identified to follow two processes: a lower valence intermediate U(V) was initially formed at the potential of ca. ?0.2 V(vs. Ag wire). Then, further deposition of UO2 was followed at around ?0.8 V. Little amount of water (1–4 wt%) in C4MimCl, however, has an effect on the U(VI) reduction by changing the current density of the redox reaction and the diffusion coefficient of U(VI) in C4MimCl. The deposited product by potentiostatic electrolysis on the surface of stainless steel electrode was characterized by the scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) methods. Although the electrodeposited black film was amorphous, the electrochemical reduced product of U(VI) can be still confirmed to be UO2 by XRD after the crystallization of the amorphous deposits at 1,073 K in nitrogen atmosphere. 相似文献
2.
Shi WQ Hu J Zhao W Su XY Cai H Zhao YF Li YM 《Journal of mass spectrometry : JMS》2006,41(9):1205-1211
Upon exposure to ionizing radiation, DNA undergoes a variety of modifications including the production of a covalent bond between the nucleobase thymine and aromatic amino acids. In this work, electrospray ionization-mass spectrometry(ESI-MS) was used to identify the gamma radiation-induced covalent cross-linking of model peptides (sequence YPPW and pYPPW) with the nucleobase thymine. Tandem electrospray ionization-mass spectrometry (ESI-MSn) was employed to investigate the cross-linking sites. The results showed that irrespective of whether tyrosine was phosphorylated or not, the nucleobase thymine was cross-linked with the tryptophan residue. Possible cross-linking mechanisms are proposed by investigating the related mass peaks. 相似文献
3.
4.
5.
6.
看似宁静的太阳上存在着诸多活动现象,其中的爆发活动,包括耀斑(solar flares)和日冕物质抛射(CMEs),是太阳系内最剧烈的能量释放,也是造成空间环境和空间天气变化的最主要因素。磁场重联一直被认为是其背后的驱动力,然而确凿的证据一直没有找到。现在,新一代观测卫星太阳动力学天文台(SDO)终于记录到了完整可信的日冕重联过程。文章中我们简要回顾太阳爆发的研究历史,介绍最新的研究成果,并讨论将来的研究重点。 相似文献
7.
8.
Multiwalled carbon nanotubes (MWCNTs) were used as a novel kind of solid-phase extraction adsorbents in this work as well as an analytical method based on MWCNTs solid-phase extraction (SPE) combined with high-performance liquid chromatography (HPLC) was established for the determination of polycyclic aromatic hydrocarbons (PAHs), some of which belong to typical persistent organic pollutants (POPs) owing to their carcinogenicity and endocrine disrupting activity. Several conditions that probably affected the extraction efficiency including the eluent volume, sample flow rate, sample pH and the sample volume were optimized in detail. The characteristic data of analytical performance were determined to investigate the sensitivity and precision of the method, and the method was applied to the determination of PAHs in environmental water samples such as river water sample, tap water sample and wastewater sample from the constructed wetland effluent. The experimental results indicated that there were excellent linear relationship between peak area and the concentration of PAHs over the range of 0.04-100 microg L(-1), and the precisions (RSD) were 1.7-4.8% under the optimal conditions. The detection limits of proposed method for the studied PAHs were 0.005-0.058 microg L(-1) (S/N=3). The recoveries of PAHs spiked in environmental water samples ranged from 78.7 to 118.1%. It was concluded that MWCNTs packed cartridge coupled with HPLC was an excellent alternative for the routine analysis of PAHs at trace level. 相似文献
9.
Thixotropic properties of aqueous suspensions containing cationic starch and aluminum magnesium hydrotalcite-like compound 总被引:3,自引:0,他引:3
The rheological properties of aqueous suspensions consisting of cationic starch (CS) and positively charged aluminum magnesium hydrotalcite-like compound (HTlc) were investigated. Special emphasis was placed on the thixotropic phenomena. With the increase of mass ratio (R) of HTlc to CS, the equilibrium viscosity (eta(eq)) and the consistency coefficient (m) values of the suspensions increase in the range of neutral and alkaline pH (higher than 6.5) while decrease in the range of acid pH (lower than 6.5). With the increase of pH value, the eta(eq) and m values of the suspensions in the R range of 0-0.08 studied increase initially and then decrease, appearing a maximum value at about pH 7.41+/-0.25. The CS/HTlc suspensions display viscid character and the yield point of the suspensions was not observed except the suspension with R=0.08 in the pH range of 7.66-9.70, which showed a yield point and viscoelasticity. The CS/HTlc suspensions may display different thixotropic types: negative, complex or positive thixotropy, depending on pH and R value. The thixotropic type of the CS/HTlc suspension may be transformed from negative (pure CS solution), through complex (R=0.02), into positive thixotropy (R=0.05 and 0.08) with the increase of R in the studied R range of 0-0.08, and the thixotropic strength of the suspensions increases initially and then decreases with pH value in the pH range studied. The mechanism of the thixotropic phenomenon is discussed. 相似文献
10.
Wei-Qun Yang Wei Tang Xiao-Jun Huang Jian-Guo Song Yue-Yue Li Yu Xiong Chun-Lin Fan Zhen-Long Wu Ying Wang Wen-Cai Ye 《Molecules (Basel, Switzerland)》2021,26(19)
A phytochemical investigation on the roots of medicinal plant Eurycoma longifolia resulted in the isolation of 10 new highly oxygenated C20 quassinoids longifolactones G‒P (1–10), along with four known ones (11–14). Their chemical structures and absolute configurations were unambiguously elucidated on the basis of comprehensive spectroscopic analysis and X-ray crystallographic data. Notably, compound 1 is a rare pentacyclic C20 quassinoid featuring a densely functionalized 2,5-dioxatricyclo[5.2.2.04,8]undecane core. Compound 4 represents the first example of quassinoids containing a 14,15-epoxy functionality, and 7 features an unusual α-oriented hydroxyl group at C-14. All isolated compounds were evaluated for their anti-proliferation activities on human leukemia cells. Among the isolates, compounds 5, 12, 13, and 14 potently inhibited the in vitro proliferation of K562 and HL-60 cells with IC50 values ranging from 2.90 to 8.20 μM. 相似文献