Enhanced thermal stability of zinc-based titanate (dielectric) ceramics prepared by the modified sol-gel route

A multi-component substitution of Co and Ni was incorporated into ZnTiO3 to form pure hexagonal Zn1-x(Co1/2Ni1/2)xTiO(3) (x = 0,0.8,0.9,1.0) dielectric ceramic powders by a modified sol-gel route, following heat treatments at 600 degrees C for 3 h and at 800 degrees C for 6 h. Differential scanning calorimetry measurements revealed that the order of increasing thermal stability of solid solution compound Zn1-x(Co1/2Ni1/2)(x)TiO3 was ZnTiO3 (945 degrees C), Zn0.1Ni0.9TiO3 (1346 degrees C), Zn-0.1(Co1/2Ni1/2)(0.9)TiO3 (1390 degrees C), and Zn0.1Co0.9TiO3 (> 1400 degrees C). Both the dielectric constant and loss tangent reached a maximum at x = 0.8 and then decreased with solubility, x, and measurement frequency.

Electrochemical detection of DNA immobilized on gold colloid particles modified self-assembled monolayer electrode with silver nanoparticle label

The target DNA was immobilized successfully on gold colloid particles associated with a cysteamine monolayer on gold electrode surface. Self-assembly of colloidal An onto a cysteamine modified gold electrode can enlarge the electrode surface area and enhance greatly the amount of immobilized single stranded DNA (ssDNA). The electrontransfer processes of [Fe(CN)(6)](4)-/[Fe(CN)(6)](3-) on the gold surface were blocked due to the procedures of the target DNA immobilization, which was investigated by impedance spectroscopy. Then single stranded target DNA immobilized on the gold electrode hybridized with the silver nanoparticle-oligonucleotide DNA probe, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution, and the indirect determination of the released solubilized Ag-1 ions by anodic stripping voltammetry (ASV) at a carbon fiber microelectrode. The results show that this method has good correlation for DNA detection in the range of 10-800 pmol/1 and allows the detection level as low as 5 pmol/1 of the target oligonucleotides.

Bright electroluminescence from a new conjugated dendrimer

Photoluminescence and electroluminescence from a new conjugated dendrimer consisting of three distyrylbenzene units linked by a central nitrogen atom as core and meta-linked biphenyl units as dendrons were investigated. Bright electroluminescence was realized by using bilayer devices with blurred interface, which were fabricated by sequentially spin-coating a neat dendrimer and a dendrimer doped with 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD). By optimizing the concentration of PBD, the maximum brightness and EL quantum efficiency reach 4100 cd/m(2) and 0.10%, respectively.

Methanol tolerant FeTPP-Pt/C Co-catalysts for the electroreduction of oxygen

It was found for the first time that iron tetraphenylporphyrin (FeTPP)-Pt/C showed the good activity for the electroreduction of oxygen and methanol tolerant ability. Their performances were related to the heat-treatment temperature.

Observations on photochemical fluorescence enhancement of the terbium(III) sparfloxacin system

Fluorescence of terbium(III) was sensitized when excited in the presence of sparfloxacin (SPFX) in the aqueous solution because a Tb(III)-SPFX complex was formed. The sensitized fluorescence was further enhanced when this system was exposed to 365 nm ultraviolet light. By the spectral properties and contrast experiments, it is proved that irradiation makes this system undergo photochemical reactions and a new terbium complex which is more favorable to the intramolecular energy transfer is formed. The mechanism of photochemical fluorescence enhancement of the Tb(III)-SPFX system is discussed and a new sensitive and selective photochemical fluorimetry for the determination of SPFX is established. Under the optimum conditions, the linear range is 1.0-50 x 10(-7) M for SPFX, the detection limit is 3.0 x 10(-9) M and the R.S.D. for 5.0 x 10(-7) M SPFX is 1.3% (n = 9). Without any pretreatment the recovery of SPFX in human urine was determined with satisfaction. (C) 1999 Elsevier Science B.V. All rights reserved.

稀土混合共发光效应的研究——(铽-钆-钇)-铕-噻吩甲酰三氟丙酮-氯化甲基三烷基铵-Triton X-100荧光体系

本文研究了铽(Tb)、钇(Y)、钆(Gd)及它们的混合物对铕(Eu)-噻吩甲酰三氟丙酮(TTA)-氯化甲基三烷基铵(N_(263))-Triton X-100体系的共发光效应,发现稀土离子混合物的共发光效应具有线性加和性,用混合共发光体系不仅能保持单个稀土离子的共发光体系的增敏性,而且抗干扰能力增强,并经过实际样品分析的验证,结果令人满意。

稀土三氟乙酸络合物的快原子轰击质谱研究

本文首次报道Ln(OOCCF_3)_3(Ln=Pr、Nd、Sm、Eu、Gd、Tb、Ho、Er、Tm、Yb、Lu在甘油(G)中的正负离子FAB谱、总结了其离子特征。通过亚稳分析、探讨了某些离子的碎裂方式,提出了Ln(Ⅱ)→Ln(Ⅰ)可能的还原变价机制。

PRELIMINARY STUDIES ON CRYOPRESERVATION OF SYDNEY ROCK OYSTER (SACCOSTREA GLOMERATA) LARVAE

In this study several parameters critical to the success of cryopreserving Sydney rock oyster (Saccostrea glomerata) larvae were investigated. They were: (1) cryoprotectants (10% dimethyl sulfoxide and 10% propylene glycol). (2) freezing protocols (with or without the seeding step). (3) larval concentrations (1,000, 3,000, 5,000, 10,000, 30,000 individuals mL(-1)). and (4) larval ages (6, 12, 24, 48 and 96 h old). The survival rates were determined as percentages of postthaw larvae performing active movements for the 6 and 12 h larvae or active cilia movement for the 24, 48 and 96 h larvae. Analyses showed that the difference in survival rates between different age classses was significant in all the experiments conducted, with the maximum survival rate being achieved in the 24-h-old larvae the postthaw survival rates of larvae cryopreserved with 10% dimethyl sulfoxide (93.1 +/- 0.2%) were significantly higher (P < 0.001) that those with 10% propylene glycol (81.5 +/- 0.4%). Differences in postthaw survival rates between different concentrations (1,000 30,000 individuals mL(-1)) were not significant within each of the three larval age classes (6-, 12-, and 24-h-old ) used.

江河源不同区域紫花针茅草原群落特征

选择江河源区玛多、曲麻莱、同德3地区的典型紫花针茅（Stipa purpurea）草原为研究对象，采用样线和样方相结合的方法调查群落，初步分析了江河源区紫花针茅草原的群落特征。结果表明：1）所调查紫花针茅草原群落是物种组成比较简单、北温带分布的属为主体的草原群落。2）所有样线经聚类分析可归为3个群落类型：紫花针茅十二裂委陵菜（Potentilla bifurca）群落（Ⅰ）、紫花针茅＋高山嵩草（Kobresia pygmaea）群落（Ⅱ）、紫花针茅＋川青早熟禾（Poa indattenuata）群落（Ⅲ），且各群落分布于不同区域。虽然这3个群落类型都是典型的紫花针茅群落，但各自的群落结构还是存在一定差异，群落相似性分析结果表明群落Ⅰ和Ⅱ的相似性较高，群落Ⅰ和Ⅲ的相似性较低。3）紫花针茅草原的群落分布呈现出小尺度区域同质性和人尺度异域异质性的特点。4）所调查紫花针茅草原群落的均匀度指数、Shannon-Wiener指数和Simpson指数间以及它们和纬度间均呈显著相关。各α多样性指数在3个地区的群落间表现出基本一致的变化规律，按均匀度指数、Shannon-Wiener指数和Simpson指数从大到小的顺序依次是：群落Ⅱ〉群落Ⅲ〉群落Ⅰ。

中国针茅属植物的地理分布

本文论述了中国针茅属植物的地理分布、生态特点及其与植被分布的关系。中国针茅属有32种1亚种及4变种,据该属各个种所处环境中的气候和土壤等因素的变化,不同种的分布也各异。属的分布区的类型属于吴征镒(1979)的中国植物区系分区的泛北极植物区中的6个植物亚区,即亚洲荒漠植物亚区,欧、亚森林植物亚区,青藏高原植物亚区,中国-喜马拉雅植物亚区,欧、亚草原植物亚区及中国-日本森林植物亚区。

一个CIMS环境下的基于范例的船体装配CAPP系统

本文介绍了一个 CIMS环境下的基于范例的船体装配 CAPP系统 .包括 :CAPP系统在渤海造船厂 CIMS工程中的地位 ,基于范例的工艺规划 (范例的表达 ,范例的索引、存储、检索和适应 ) ,工艺定额和材料定额制定 ,分系统之间的信息集成 .系统采用 Power Builder和 SQL Server数据库中的 SQL语言编写 .目前 ,船体装配 CAPP系统已经在渤海造船厂的微机上连网运行

The active sites in different TS-1 zeolites for propylene epoxidation studied by ultraviolet resonance Raman and ultraviolet visible absorption spectroscopies

The titanium species in four kinds of titanium-containing MFI zeolites have been studied by ultraviolet (UV)-Raman and ultraviolet visible (UV-Vis) absorption spectroscopies and by the epoxidation of propylene with diluted H2O2 solution (30%). UV-Raman spectroscopy is proved to be a suitable means to estimate qualitatively the framework titanium in TS-l zeolites. Based on the comparison of the relative intensity ratio I-1125/I-380 of UV-Raman spectra, the TS-1(conv.) sample synthesized hydrothermally by the conventional procedure shows the highest amount of framework titanium. UV-Vis spectroscopy reveals that besides minor anatase. titanium species are mainly tetrahydrally coordinated into the framework for TS-l(conv.) or the Ti-ZSM-5 sample prepared by gas-solid reaction between deboronated B-ZSM-5 and TiCl4 vapor at elevated temperatures. For the TS-1(org.) and TS-1(inorg.) samples synthesized hydrothermally using tetrapropylammonium bromide (TPABr) as template and tetrabutylorthotitanite (TBOT) and TiCl3 as titanium source, respectively, the presence of mononuclear and isolated TiOx species which are proposed to bond to the zeolite extraframework is observed. In addition to the framework titanium species, these isolated TiOx species are assumed to be also active for propylene epoxidation.

Summarizing Qualitative Behavior from Measurements of NonlinearsCircuits

This report describes a program which automatically characterizes the behavior of any driven, nonlinear, electrical circuit. To do this, the program autonomously selects interesting input parameters, drives the circuit, measures its response, performs a set of numeric computations on the measured data, interprets the results, and decomposes the circuit's parameter space into regions of qualitatively distinct behavior. The output is a two-dimensional portrait summarizing the high-level, qualitative behavior of the circuit for every point in the graph, an accompanying textual explanation describing any interesting patterns observed in the diagram, and a symbolic description of the circuit's behavior which can be passed on to other programs for further analysis.