游人对专类植物景观的行为偏好研究

选取北京植物园8个专类植物景观区域,使用行为观察法观测记录游人行为,用行为地图法及列联表分析游人的行为偏好,研究游人行为与专类植物景观之间的关系.研究结果表明,在专类植物景观区域中,拍照、穿行、散步和观景等与优美的专类植物景观环境有着紧密联系的行为活动最多.游人偏好于可达性强、有集中展示效果的专类花展景观,以及观赏期长...     

PLA镀铝膜/牛皮纸复合食品包装材料制备及性能研究

目的 分析聚乳酸（Polylactic Acid,PLA）镀铝膜与牛皮纸复合对牛皮纸基复合材料性能的影响,研究该纸基复合包装对提升中草药薄荷保鲜效果的作用,探讨其在农产品包装保鲜领域的应用潜力。方法 通过PLA镀铝膜与牛皮纸复合,增强牛皮纸的阻隔性能和力学性能,弥补单纯牛皮纸阻隔和力学性能较差的缺点。结果 与PLA镀铝膜复合后的牛皮纸基复合材料力学性能、阻隔性能均得到显著提升;复合包装对薄荷的应用研究测试表明,该复合材料具有良好的阻隔性能和防霉性能,且符合环保要求。结论 PLA镀铝膜/牛皮纸复合包装能有效降低薄荷的质量损失率,维持其颜色和新鲜度,延长保鲜期限。感官评价结果表明,牛皮纸基复合包装材料在维持薄荷的颜色、完整度和脆性方面表现更佳。     

非人类物种的城市化:动物也是地球上的一员

提出在日益城市化进程中人类与非人类物种之间关系的4种推测。由于非人类物种也在快速城市化,它们的空间条件大部分都是由人类为自己所构建,这可以集中并强化拉图尔的生物共生理念。风景园林师应该理清自己工作的政治影响,而其中的一种方法是处理物种之间微妙而脆弱的相互关系。当然,采用未经验证的新自由主义设计在大多数情况下对非人类物种都会带来特殊的破坏性后果。本文使用\"基础设施\"模型探讨不同的生物群体之间如何相互影响彼此的命运。     

四能级动态雪崩上转换过程的计算分析

通过建立四能级雪崩上转换系统的速率方程,分析和讨论了雪崩上转换的动态过程及其特点     

Electrocatalytic oxidation of norepinephrine at a reduced C60-[dimethyl-(β-cyclodextrin)]2 and Nafion chemically modified electrode

The reduced C₆₀-[dimethyl-(β-cyclodextrin)]₂/Nafion chemically modified electrode is demonstrated to catalyze the electrochemical response of norepinephrine (NE) by cyclic voltammetry. A pair of well-defined redox waves were obtained and the calculated standard rate constant (k_s) is 4.4×10⁻³ cm s⁻¹ at this reduced CME, indicating that the reduced C₆₀-[dimethyl-(β-cyclodextrin)]₂ can act as promoter to the electron transfer of NE.     

钪酸盐阴极发射物质相的研究

用多晶X射线衍射方法,研究钪酸盐阴极发射材料在烧结过程中物理化学变化。由BaO-CaO-Al2O3-Sc2O3组成的发射材料中,在10001300℃内,是Ba-Al-O和Ba-Sc-O体系与CaO的混合物;在13001500℃内,是Ba-Al-O和Ba-Sc-O体系互溶生成热力学上的亚稳定态的Ba-Al-Sc-O固溶体。先形成组成约为5BaO-Al2O3-Sc2O3物相,属正交晶系,a=9.725(2),b=8.698(3),c=6.152(3);最后生成组成约为4BaO-Al2O3-0.5Sc2O3物相,属四方晶系,a=14.4996(19),b=4.4996(19),c=5.0265(8).CaO呈游离状态。     

整流装置滤除谐波的措施

对多相整流电路的高次谐波进行了分析，并指出其对节能工作及微机的集散系统的干扰，经过分析提出了消除谐波的措施，通过应用实例介绍了不同条件时可采取的不同消除办法。     

精神激励的效能研究

人类行为产生于人类动机，人类动机根源于人类需要．根据职工的不同需要，激发职工相应的行为动机，创造和维护一种有利于调动积极性的环境，是科学地应用精神激励，并使之产生显著成效的基本方法．     

Ferrocene-filled single-walled carbon nanotubes

Ferrocene molecules are successfully introduced into the inner hollow space of Single-walled carbon nanotubes (SWNTs) to get ferrocene-filled SWNTs (Fc@SWNTs). This nanohybrid material was carefully characterized by high resolution microscopy, FTIR spectrum, and Cyclic voltammetry (CV). This new material may not only act as air stable n-type field-effect transistors based on nanotubes, but it may also be employed as building blocks for various devices based on the redox activity of ferrocene. What’s more, upon high temperature annealing, the encapsulated ferrocene molecules will decompose and change into interior tubes, forming double-walled carbon nanotubes (DWNTs). This provides convincing evidence that ferrocene molecules are inserted into the hollow cavities SWNTs. This result also presented a controllable way to synthesize DWNTs.     

Electrochemical DNAzyme sensor for lead based on amplification of DNA-Au bio-bar codes

An electrochemical DNAzyme sensor for sensitive and selective detection of lead ion (Pb(2+)) has been developed, taking advantage of catalytic reactions of a DNAzyme upon its binding to Pb(2+) and the use of DNA-Au bio-bar codes to achieve signal enhancement. A specific DNAzyme for Pb(2+) is immobilized onto an Au electrode surface via a thiol-Au interaction. The DNAzyme hybridizes to a specially designed complementary substrate strand that has an overhang, which in turn hybridizes to the DNA-Au bio-bar code (short oligonucleotides attached to 13 nm gold nanoparticles). A redox mediator, Ru(NH3)6(3+), which can bind to the anionic phosphate of DNA through electrostatic interactions, serves as the electrochemical signal transducer. Upon binding of Pb(2+) to the DNAzyme, the DNAzyme catalyzes the hydrolytic cleavage of the substrate, resulting in the removal of the substrate strand along with the DNA bio-bar code and the bound Ru(NH3)6(3+) from the Au electrode surface. The release of Ru(NH3)6(3+) results in lower electrochemical signal of Ru(NH3)6(3+) confined on the electrode surface. Differential pulse voltammetry (DPV) signals of Ru(NH3)6(3+) provides quantitative measures of the concentrations of Pb(2+), with a linear calibration ranging from 5 nM to 0.1 microM. Because each nanoparticle carries a large number of DNA strands that bind to the signal transducer molecule Ru(NH3)6(3+), the use of DNA-Au bio-bar codes enhances the detection sensitivity by five times, enabling the detection of Pb(2+) at a very low level (1 nM). The DPV signal response of the DNAzyme sensor is negligible for other divalent metal ions, indicating that the sensor is highly selective for Pb(2+). Although this DNAzyme sensor is demonstrated for the detection of Pb(2+), it has the potential to serve as a general platform for design sensors for other small molecules and heavy metal ions.