Heat capacities and thermodynamic properties of chrysanthemic acid

The heat capacities of chrysanthemic acid in the temperature range from 80 to 400 K were measured with a precise automatic adiabatic calorimeter. The chrysanthemic acid sample was prepared with the purity of 0.9855 mole fraction. A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, T-m, enthalpy and entropy of fusion, Delta(fus)H(m), Delta(fus)S(m), were determined to be 390.741 +/- 0.002 K, 14.51 +/- 0.13 kJ mol(-1), 37.13 +/- 0.34 J mol(-1) K-1, respectively. The thermodynamic functions of chrysanthemic acid, H-(T)-H-(298.15), S-(T)-S-(298.15) and G((T))-G((298.15)) were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min(-1) confirmed that the thermal decomposition of the sample starts at ca. 410 K and terminates at ca. 471 K. The maximum decomposition rate was obtained at 466 K. The purity of the sample was determined by a fractional melting method.

黄土高原地区粮食生产趋势及其策略研究

根据建国以后黄土高原粮食生产进程经历了振荡期 (1 949— 1 964)、徘徊期 (1 965— 1 983年 )、增长期 (1 984— 1 997)三个阶段 ,分析了粮食发展的趋势 ,预测了 2 0 0 0— 2 0 2 3年七个不同年份全区和分区粮食的总产 ,并在对黄土高原粮食生产进行综合考察与定位试验的基础上 ,结合区域各地粮食生产及地貌类型、土壤侵蚀程度、生产环境、农业生产条件和国家粮食政策 ,提出了粮食可持续发展的经济对策和技术对策

黄土高原粮食发展趋势及策略研究

根据建国以后黄土高原地区粮食生产进程经历了振荡期 (1 949～ 1 964年 )、徘徊期 (1 965～ 1 983年 )、增长期(1 984～ 1 997年 )三个阶段 ,分析了粮食发展趋势 ,预测了 2 0 0 0～ 2 0 30年七个不同年份全区和分区粮食的总产 ,并在对黄土高原粮食生产进行综合考察与定位试验的基础上 ,结合区域内各地粮食生产及地貌类型、土壤侵蚀程度、生态环境、农业生产条件和国家粮食政策 ,提出了粮食可持续发展的经济对策和技术对策

子午岭不同土地利用方式对土壤性质的影响

通过野外调查和室内分析相结合的方法,研究子午岭次生林区不同土地利用方式下的土壤性质状况,分析土地利用状况与土壤质量之间的关系,结果表明:不同土地利用方式表层土壤有机质、全氮、全磷、pH值、脲酶、蔗糖酶和碱性磷酸酶含量或活性差异显著,农地主要土壤养分含量和酶活性较低,林地则较高。除pH值外,不同利用方式下土壤养分和酶活性均随土层深度的增加而逐渐减小。除土壤pH值外,不同利用方式下土壤有机质、全氮、全磷、铵态氮、脲酶、蔗糖酶、碱性磷酸酶和过氧化氢酶之间呈显著或极显著正相关性。以林地为对照的土壤退化指数表明农用地和撂荒翻耕地土壤质量退化显著,其表层(0～20cm)土壤退化指数分别为44.86%和43.10%;撂荒未翻耕地深层(20～130cm)土壤质量则有所提高。

水稻叶片光谱对亚铁胁迫的响应

在湖泊富营养化治理过程中,除了要注意控制氮、磷的输入,还应考虑铁(Fe)的调控作用.本文基于"Fe假说",探索性地将植物光谱效应应用于湖泊水体富营养化遥感预警机制研究.在水培条件下分析了亚铁(Fe2+)胁迫对水稻(Oryza sativaL.)体内Fe含量、叶绿素浓度及可见-近红外特征光谱的影响,并对其相关关系进行了深入探讨;同时,应用3个光谱定量化指标A1(Fe2+胁迫水稻叶片在460~670nm波段反射率变化积分值)、A2(Fe2+胁迫水稻叶片在760~1000nm波段反射率变化积分值)、S(Fe2+胁迫水稻叶片光谱曲线红边"蓝移"强度)分别建立了水稻叶片Fe含量与叶片光谱之间的定量相关关系模型.结果表明,随培养液中Fe2+浓度的升高,水稻体内Fe含量逐渐增加,叶绿素浓度降低,叶片光谱反射率在可见光波段升高,在近红外波段降低,同时红边发生"蓝移".水稻叶片的3个光谱指标A1,A2,S与叶片中Fe含量都具有显著相关性,相关系数分别为0.933(P<0.01),-0.965(P<0.01)和0.946(P<0.01),且A1,A2和S3个参数都能够较好地模拟(复相关系数R2>0.96)和估测水稻叶片Fe含量.

Amplified electrochemical aptasensor taking AuNPs based sandwich sensing platform as a model

Here, we report a sensitive amplified electrochemical impedimetric aptasensor for thrombin, a kind of serine protease that plays important role in thrombosis and haemostasis. For improving detection sensitivity, a sandwich sensing platform is fabricated, in which the thiolated aptamers are firstly immobilized on a gold substrate to capture the thrombin molecules, and then the aptamer functionalized Au nanoparticles (AuNPs) are used to amplify the impedimetric signals.

Ab initio study on the electronic and mechanical properties of ReB and ReC

The structural, electronic, and mechanical properties of ReB and ReC have been studied by use of the density functional theory. For each compound, six structures are considered, i.e., hexagonal WC, NiAs, wurtzite, cubic NaCl, CsCl, and zinc-blende type structures. The results indicate that for ReB and ReC, WC type structure is energetically the most stable among the considered structures, followed by NiAs type structure. ReB-WC (i.e., ReB in WC type structure) and ReB-NiAs are both thermodynamically and mechanically stable. ReC-WC and ReC-NiAs are mechanically stable and becomes thermodynamically stable above 35 and 55 GPa, respectively. The estimated hardness from shear modulus is 34 GPa for ReB-WC, 28GPa for ReB-NiAs, 35GPa for ReC-WC and 37GPa for ReC-NiAs, indicating that they are potential candidates to be ultra-incompressible and hard materials.

Stereoselective polymerization of rac-lactide using a monoethylaluminum Schiff base complex

A monoethylaluminum Schiff base complex (2) with formula LA1Et (L = N,N'-(2,2-dimethylpropylene)bis(3,5-di-tei-t-butylsalicylideneimine) was synthesized and employed for the stercoselective ring-opening polymerization of rac-lactide (rac-LA). The complex 2 was characterized by nuclear magnetic resonance, crystal structure, and elemental analysis. It contains a five-coordinate aluminum atom with distorted trigonal bipyramidal geornetry in the solid state. In the presence of 2-propanol, 2 showed high stereoselectivity for the polymerization of rac-LA. The polymerization yielded crystalline poly(rac-LA) with a high melting temperature (193-201 degreesC). NMR, differential scanning calorimetry, and wide-angle X-ray diffraction indicated that the poly(rac-LA) was highly isotactic, and a stereocomplex was formed between poly-L- and poly-D-lactide block sequences. By the analysis of electrospray-ionization mass spectrometry and H-1 NMR, the polymer was demonstrated to be endcapped in both terminals with an isopropyl ester and a hydroxy group, respectively. The polymerization was of first order in rac-LA concentration. The relationship between the rac-LA conversion and molecular weights of the polymer was linear so that the polymerization could be well controlled.

White electrolumineseence from a single-polymer system with simultaneous two-color emission: Polyfluorene as the blue host and a 2,1,3-benzothiadiazole derivative as the orange dopant on the main chain

New single-polymer electroluminescent systems containing two individual emission species - polyfluorenes as a blue host and 2,1,3-benzothiadiazole derivative units as an orange dopant on the main chain - have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue(lambda(max) = 421 nm/445 nm) and orange emission (lambda(max) = 564 nm)from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light-emitting diodes (PLEDs) based on the single-polymer systems has been investigated. The introduction of the highly efficient 4,7-bis(4-(N-phenyl-N-(4-methylphenyl)amino)phenyl)-2,1,3-benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single-layer device fabricated in air (indium tin oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure-white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m(-2), luminance efficiency of 7.30 cd A(-1), and power efficiency of 3.34 lm W-1 can be obtained.

Cation selectivity of perfluorosulfonate polymer

Selectivity coefficient measurement has been performed for K+,Ni2+,Fe3+ with Nafion 117 perfluorosulfonate polymer as-received forms. The results show that a linear Nernst response is exhibited for H+,K+,Pb2+,Ni2+,Co2+,Fe3+, and the ion selectivity coefficient of Nafion membrane for KC is better than Ni2+ and Fe3+.

全氟磺酸膜的离子选择性

研究了Nafion117膜(一种全氟磺酸膜)对阳离子的选择性,测定了含K~+、Ni~(2+)及Fe~(3+)的Nafion 117膜的离子选择性系数,实验发现含H~+、K~+、Pb~(2+)、Ni~(2+)、Co~(2+)、Fe~(3+)等离子的膜都能较好符合Nemst响应.膜对一价离子的选择性优于二价及三价离子.

沸石微孔材料中Ce（Ⅲ）对Tb（Ⅲ）的敏化发光

采用水相离子交换法合成出双掺Ｃｅ（Ⅲ）、Ｔｂ（Ⅲ）沸石材料，讨论了光谱特征和浓度猝灭。在沸石基质中观察到稀土离子间的能量传递，通过荧光光谱和荧光寿命等实验技术，系统地研究了能量传递过程，其传递机理主要是无辐射多极子近场力作用。

IMPROVEMENT OF SELECTIVITY WITH NUMERICAL DERIVATIVE TECHNIQUES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

One of the most attractive features of derivative spectrometry is its higher resolving power. In the present power, numerical derivative techniques are evaluated from the viewpoint of increase in selectivity, the latter being expressed in terms of the interferent equivalent concentration (IEC). Typical spectral interferences are covered, including flat background, sloped background, simple curved background and various types of line overlap with different overlapping degrees, which were defined as the ratio of the net interfering signal at the analysis wavelength to the peak signal of the interfering line. the IECs in the derivative spectra are decreased by one to two order of magnitudes compared to those in the original spectra, and in the most cases, assume values below the conventional detection limits. The overlapping degree is the dominant factor that determines whether an analysis line can be resolved from an interfering line with the derivative techniques. Generally, the second derivative technique is effective only for line overlap with an overlapping degree of less than 0.8. The effects of other factors such as line shape, data smoothing, step size and the intensity ratio of analyte to interferent on the performance of the derivative techniques are also discussed. All results are illustrated with practical examples.

用时间分辨荧光技术分析稠环芳烃

本文讨论了利用时间相关单光子计数技术中荧光衰减曲线解卷积得到的荧光寿命和幅度常数来分析多环芳烃的适用性和应用前景。实验表明荧光寿命是荧光物质的特征参数,幅度常数在较大范围内与浓度有线性关系。当多组分的荧光寿命有3～4纳秒差值时,可不经分离进行定性、定量分析。