Examples of compactλ-hypersurfaces in Euclidean spaces

In this paper,we first construct compact embeddedλ-hypersurfaces with the topology of torus which are calledλ-torus in Euclidean spaces?n^+1.Then,we give many compact immersedλ-hypersurfaces in Euclidean spaces?n^+1.     

硫代钼酸盐和硫代钨酸盐的合成性质和取代反应的研究

本文提出了在水或水/醇溶液中[NH_4]_2[MO_nS_(4-n)](M=Mo、W,n=0-2)进行取代反应的方法。用该方法合成出[X]_2[MO_nS_(4-n)](X=(n-Bu)_4N、Ph_4P、py—C_(16)H_(33)共18个化合物,其中11个为新化合物,并采用元素分析、红外光谱、电子光谱和X-粉末衍射等方法对这些化合物进行了表征。     

Headspace Solid-phase Microextraction–Gas Chromatographic–Mass Spectrometric Analysis of the Essential Oils of Two Traditional Chinese Medicines, Angelica pubescens and Angelica sinensis

Angelica pubescens and Angelica sinensis belong to the Umbelliferae family and both are used as traditional Chinese medicines. In the present study, headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS) was used for the analysis of the volatile constituents present in their roots. Eighty-seven compounds in Angelica pubescens and thirty-six compounds in Angelica sinensis were identified by GC-MS. Their relative contents were calculated by the peak area ratio. HS-SPME was compared to steam distillation (SD) by analyzing the volatile constituents of Angelica sinensis root. A good agreement between results obtained with both techniques was found. As a conclusion, HS-SPME is a powerful tool for determining the volatile constituents present in the TCMs.     

牛血清白蛋白在NVP/HEMA无规共聚物水凝胶上的吸附研究

合成了不同含水量的N-乙烯吡咯烷酮(NVP)／甲基丙烯酸-β-羟乙酯(HEMA)共聚物水凝胶．研究了温度、pH值，蛋白质初浓度及离子强度等因素对牛血清白蛋白吸附性能的影响．采用紫外分光光度法测定BSA的吸附量．结果表明，蛋白质初浓度越高．温度越高，离子强度越大；蛋白质内部更多的疏水性氧基酸残基暴露于外部．吸附量增加：在等电点pH=4．7附近蛋白质沉积量最大．     

羧酸铜催化反应的研究——Ⅰ.羧酸铜催化醛肟转变为睛

本文报道了在多种羧酸铜催化下,醛肟在含有氰基的溶剂中(如CH_3CN、CH_3OCH_2CH_2CN等),均可脱水转变成相应的腈。反应条件温和,产率较高。具有不同空间和电性效应取代基的羧酸铜对反应的产率影响不大。实验中还发现溶剂乙腈参与了上述反应。     

Effects of EG and MoSi2 on thermal degradation of intumescent coating

An intumescent flame retardant coating was prepared with resin, solvent and flame retardant system composed of ammonium polyphosphate-APP, pentaerythritol-PER and melamine-MEL. The modifiers such as molybdenum disilicide (MoSi₂) and expandable graphite (EG) were used to improve the performances of the APP-PER-MEL coating. The effects of EG, MoSi₂ and MoSi₂/EG on the fireproofing time and char formation of the coating were investigated by using heat insulation test, thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electric microscope (SEM). The results showed that by adding modifiers, the fireproofing time was prolonged and char formation rate was evidently enhanced. The largest improvement was achieved with 9 wt.% MoSi₂/5 wt.% EG, XPS analysis indicated that the performance of anti-oxidation of the coating was improved by adding EG and MoSi₂, and SEM images showed that a good synergistic effect was obtained through a ceramic-like layer produced by MoSi₂ covered on the surface of “open-cellular” structural char.     

In situ real-time study buckling behavior of boron nitride nanotubes with axial compression by TEM

The real time analysis structure evolution of BNNT with compression showed that the formation of V-shape in the post-buckling before BNNT fracture was reversible.     

Thermodynamic and Structural Trends in Hexavalent Actinyl Cations: Complexation of Dipicolinic Acid with NpO22+ and PuO22+ in Comparison with UO22+

The complexation of NpO₂²⁺ and PuO₂²⁺ with dipicolinic acid (DPA) has been investigated in 0.1 M NaClO₄ by spectrophotometry, microcalorimetry, and single crystal diffractometry. Formation of 1:1 and 1:2 (metal/ligand molar ratio) complexes of DPA with NpO₂²⁺ and PuO₂²⁺ were identified and the thermodynamic parameters were determined and compared with those of UO₂²⁺. All three hexavalent actinyl cations form strong 1:1 DPA complexes with slightly decreasing but comparable stability constants from UO₂²⁺ to PuO₂²⁺, whereas the stability constants of the 1:2 complexes (log β₂) decrease substantially along the series (16.3 for UO₂L₂^2?, 15.17 for NpO₂L₂^2?, and 14.17 for PuO₂L₂^2? at 25 °C). The enthalpies of complexation for the 1:2 complexes become less exothermic from UO₂L₂^2? (?28.9 kJ mol^?1), through NpO₂L₂^2? (?27.2 kJ mol^?1), and to PuO₂L₂^2? (?22.7 kJ mol^?1). The trends in the thermodynamic parameters are discussed in terms of the effective charge of the cations and the steric constraints in the structures of the complexes. In addition, the features of the absorption spectra, including the wavelength and intensity of the absorption bands, are related to the perturbation of the ligand field and the symmetry of the actinyl complexes.