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911.
本文通过无水三氯化希土与等摩尔的甲基环戊二烯基钠(Cp′Na)在四氢呋喃(THF)中反应,合成了八个新的中性甲基环戊二烯基希土二氯化合物Cp′LnCl2·3THF[Ln=Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Ho(6), Er(7), Y(8)],并研究了茂环上甲基取代基对一茂二氯希土配合物分子结构及稳定性的影响。元素分析、红外光谱和质谱鉴定结果表明这八个化合物都是溶剂化的单体结构,其中配合物7的结构还用单晶X射线分析确证。 相似文献
912.
913.
The colloidal stability and core-shell structure of magnetite nanoparticles coated with alginate 总被引:1,自引:0,他引:1
The adsorption of alginate (Alg) onto the surface of in water dispersed Fe3O4 nanoparticles and zeta potential of alginate-coated Fe3O4 nanoparticles have been investigated to optimize the colloidal stability of Alg-coated Fe3O4 nanoparticles. The adsorption amount of Alg increased with the decrease of adsorption pH. The zeta potential of Fe3O4 nanoparticles shifted to a lower value after adsorption of Alg. The lower adsorption pH was the lower zeta potential of Fe3O4 nanoparticles became. The Alg-coated Fe3O4 nanoparticles were found to be stabilized by steric and electrostatic repulsions. Those prepared at pH 6 were not stable around pH 5, and those prepared at pH 4 became unstable at pH below 3.5. Alg of Mw 45 kDa was a little bit more adsorbed onto nanoparticles surface than that of Mw 24 kDa. An average Fe3O4 core size of 9.3 ± 1.7 nm was found by transmission electronic microscopy. An average hydrodynamic diameter of 30-150 nm was measured by photon correlation spectroscopy. However, an average core size of 10 nm and an average hydrodynamic diameter of 38 nm were estimated from the magnetization curve of the concentrated magnetic fluids (MFs). The maximum available saturation magnetization of MFs was about 3.5 kA/m. 相似文献
914.
通过数学方法较为精确地建立了吸收式制冷机需满足负荷要求的数学模型,确立了蒸发器冷冻水出口温度与室外温度之间的关系式。进而建立了吸收式出水温度控制系统的动态特性模型,并采用并联程序法对水温控制系统进行仿真。 相似文献
915.
We investigate the electronic and band structure for the (8; 0) single-wall carbon nanotube (SWCNT) with a europium (Eu) and
a uranium (U) atom outside by using the first-principles method with the density functional theory (DFT). The calculated band
structure (BS), total density of state (TDOS), and projected density of state (PDOS) can elucidate the differences between
the pure (8; 0) SWCNT and the nuclei outside the SWCNT. The indirect band gaps are obtained when Eu and U atom are put outside
the (8; 0) CNT; they are 0.037 eV and 0.036 eV, respectively, which is much smaller than 0.851 eV for pure CNT. Compared with
pure (8; 0) SWCNT, the bottom of the conduction band moves down by 0.383 eV and 0.451 eV with the Eu and U outside, and the
top of valence band moves up by 0.127 eV and 0.162 eV, respectively. More significantly, the top of the valence band has exceeded
the fermi-level. So, a single nucleus changes the semiconductor character of pure nanotube to semi-metal. 相似文献
916.
917.
Hofmeister series ranks the ability of salt ions in influencing a variety of properties and processes in aqueous solutions.In this review,we reexamine how these ions and some other small molecules affect water structure and thermodynamic properties,such as surface tension and protein backbone solvation.We illustrate the difficulties in interpreting the thermodynamic information based on structural and dynamic arguments.As an alternative,we show that the solvation properties of ions and proteins/small molecules can be used to explain the salt effects on the thermodynamic properties of the solutions.Our analysis shows that the often neglected cation-anion cooperativity plays a very important role in these effects.We also argue that the change of hydrogen donor/acceptor equilibrium by added cosolutes/cosolvents can be used to explain their effects on protein secondary structure denaturation/protection:those increase hydrogen donor concentrations such as urea and salts with strongly solvated cations/weakly hydrated anions tend to dissolve protein backbone acting as secondary structure denaturants,whereas those lack of hydrogen donors but rich in acceptors have the opposite effect. 相似文献
918.
919.
A rapid and sensitive method was developed and validated for the determination of MCYST (microcystin)-RR, -LR, and [Dha7] MCYST-LR in rat plasma by liquid chromatography-tandem mass spectrometry. The analytes were extracted from rat plasma by protein precipitation, followed by solid-phase extraction. Liquid chromatography with electrospray ionization mass spectrometry, operating in selected reaction monitoring (SRM) mode, was used to quantify MCYST-RR, -LR, and [Dha7] MCYST-LR in rat plasma. The recoveries for each analyte in rat plasma ranged from 70.8 to 88.7%. The calibration curve was linear within the range from 0.005 to 1.25 μg mL?1. The limit of detection were 1.4, 1.0, 0.6 ng mL?1 for MCYST-RR, -LR, and [Dha7] MCYST-LR. The overall precision was determined on three different days. The values for within- and between-day precision in rat plasma were within 15%. This method was applied to the identification and quantification of microcystins in rat plasma with acute exposure of microcystins via intravenous injection. 相似文献
920.
The hydrophilic monomer acrylamide (AM) and hydrophobic monomer styrene (St) have been directly copolymerized in a surfactant‐free aqueous emulsion with the assistance of powerful ultrasound. Fourier Transform Infrared spectrocopy (FT‐IR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) measurements revealed that copolymers of AM and St were obtained. Elemental analysis was used to calculate the composition of the copolymer. Size exclusion chromatography (SEC) measurement showed that the molecular weight (Mw) of the copolymer is 1.86 × 105 g/mol and the polydispersity index (PDI( = 2.31. The self‐assembly behavior in different solvents was investigated utilizing laser light scattering (LLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM); the copolymer film showed amphiphilicity, as measured by contact angle goniometry. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献