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分析了青藏铁路纳赤台段荒漠地区的土壤及10种典型植物的常量元素中的K、Ca、Mg、P四种元素的含量。结果表明,(1)K、ca、Mg、P四种元素在区内各种植物中的变异系数分别为0.033、0.418、0.143、0.403,Ca和Mg元素在各种植物中的含量呈正相关;(2)区内所采集到的各种植物之问K、Mg两种元素含量变化不大;(3)随着土壤深度的增加,土壤内四种矿质元素含量呈递减趋势。 相似文献
3.
以柠檬酸为螯合剂,十六烷基三甲基溴化胺为表面活性剂,通过ZrOCl2·8H2O 与对苯二甲酸 (H2BDC) 反应制备了同时具有微孔和介孔结构的Zr基金属有机骨架材料(Zr-MOF),并在超临界CO2-甲醇流体中将 Ru 负载于 Zr-MOF 上, 制备了 Ru@Zr-MOF催化剂,采用傅里叶变换红外光谱、X射线粉末衍射、透射电子显微镜、热重分析、N2吸附-脱附、X射线光电子能谱和电感耦合等离子体发射光谱对催化剂进行了表征,研究了该催化剂在苯及其同系物加氢反应中的催化性能. 结果表明,Ru纳米金属颗粒均匀地分散在Zr-MOF载体上,平均粒径约为2.3nm,在苯及其同系物的加氢反应中表现出很高的催化活性和稳定性. 相似文献
4.
Junnan Lv Yiqun Chen Honglei Pei Wenhan Yang Zhimin Li Bing Dong Yunhe Cao 《Applied biochemistry and biotechnology》2013,169(8):2326-2340
The β-mannanase gene (1,029 nucleotide) from Bacillus subtilis MAFIC-S11, encoding a polypeptide of 342 amino acids, was cloned and expressed in Pichia pastoris. To increase its expression, the β-mannanase gene was optimized for codon usage (mannS) and fused downstream to a sequence-encoding modified α-factor signal peptide. The expression level was improved by 2-fold. This recombinant enzyme (mannS) showed its highest activity of 24,600 U/mL after 144-h fermentation. The optimal temperature and pH of mannS were 50 °C and 6.0, respectively, and its specific activity was 3,706 U/mg. The kinetic parameters V max and K m were determined as 20,000 U/mg and 8 mg/mL, respectively, representing the highest ever expression level of β-mannanase reported in P. pastoris. In addition, the enzyme exhibited much higher binding activity to chitin, chitosan, Avicel, and mannan. The superior catalytic properties of mannS suggested great potential as an effective additive in animal feed industry. 相似文献
5.
Shuwen Li Zhengping Dong Honglei Yang Shujing Guo Galian Gou Ren Ren Zhejun Zhu Prof. Jun Jin Jiantai Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(7):2384-2391
A new catalyst consisting of ionic liquid (IL)‐functionalized carbon nanotubes (CNTs) obtained through 1,3‐dipolar cycloaddition support‐enhanced electrocatalytic Pd nanoparticles (Pd@IL(Cl?)‐CNTs) was successfully fabricated and applied in direct ethanol alkaline fuel cells. The morphology, structure, component and stability of Pd@IL(Cl?)‐CNTs were systematic characterized by transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), Raman spectra, thermogravimetric analysis (TGA) and X‐ray diffraction (XRD). The new catalyst exhibited higher electrocatalytic activity, better tolerance and electrochemical stability than the Pd nanoparticles (NPs) immobilized on CNTs (Pd@CNTs), which was ascribed to the effects of the IL, larger electrochemically active surface area (ECSA), and greater processing performance. Cyclic voltammograms (CVs) at various scan rates illustrated that the oxidation behaviors of ethanol at all electrodes were controlled by diffusion processes. The investigation of the different counteranions demonstrated that the performance of the IL‐CNTs hybrid material was profoundly influenced by the subtly varied structures of the IL moiety. All the results indicated that the Pd@IL(Cl?)‐CNTs catalyst is an efficient anode catalyst, which has potential applications in direct ethanol fuel cells and the strategy of IL functionalization of CNTs could be available to prepare other carbonaceous carrier supports to enhance the dispersivity, stability, and catalytic performance of metal NPs as well. 相似文献
6.
Using n-PrPPh2 as the nucleophilic catalyst, the [4+2] cycloaddition reaction of the sulfamate-derived cyclic imines with allenoates works efficiently to yield various sulfamate-fused tetrahydropyridines in high yields with excellent diastereoselectivities. Using amino acid-based bifunctional phosphine as chiral catalyst, an asymmetric [4+2] cycloaddition reaction was achieved, giving chiral sulfamate-fused tetrahydropyridines in high yields with good enantiomeric excesses. 相似文献
7.
Phosphine‐Catalyzed [3+2] Cycloaddition Reactions of Azomethine Imines with Electron‐Deficient Alkenes: A Facile Access to Dinitrogen‐Fused Heterocycles
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Zhen Li Hao Yu Honglei Liu Lei Zhang Hui Jiang Bo Wang Prof. Dr. Hongchao Guo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1731-1736
An efficient method for the phosphine‐catalyzed [3+2] cycloaddition reaction of azomethine imines with diphenylsulfonyl alkenes to give dinitrogen‐fused bi‐ or tricyclic heterocyclic compounds in high yields has been described. Moreover, two phenylsulfonyl groups installed on the heterocyclic products could be conveniently removed or transformed to other functional groups, making the reaction more useful. 相似文献
8.
Improvement of high-frequency properties of Co_2FeSi Heusler films by ultrathin Ru underlayer
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Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm.It is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient remains.The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping.As a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved. 相似文献
9.
采用共沉淀法制备了7.5%Ru/ZrO2·xH2O催化剂,运用N2物理吸附-脱附法、X射线衍射、X射线光电子能谱和高分辨透射电子显微镜等技术对催化剂进行了表征,并用于催化肉桂醛选择加氢制肉桂醇反应中,考察了温度、H2压力和溶剂对肉桂醛转化率和肉桂醇选择性的影响.结果表明,肉桂醛转化率随着温度或H2压力的升高而升高,而肉桂醇选择性则随之下降.该催化剂在极性溶剂中比在非极性溶剂中表现出更高的活性和肉桂醇选择性.尤其在极性溶剂三乙胺(Et3N)中反应活性最高,且具有较高的肉桂醇选择性.在Et3N中加入水可进一步提高反应活性和选择性.以V(Et3N)/V(H2O)=4的混合物为溶剂,在4MPa和70℃的优化条件下,反应6h,肉桂醛转化率为97.9%,肉桂醇选择性达85.2%. 相似文献
10.
针对犹豫模糊信息下的多属性决策问题,提出了余弦优化投影方法,将投影夹角定义为决策者的风险偏好,并设置了态度参数用于调节决策者的心理变化,通过灵活描述决策者的保守心理,改进了投影法仅考虑投影长度的不足,使决策者可通过投影长度和投影夹角对备选方案进行综合判断。算例验证了方法的合理性和可行性。 相似文献