Renewable-surface amperometric nitrite sensor based on sol-gel-derived silicomolybdate-methylsilicate-graphite composite material

A new type of silicomolybdate-methylsilicate-graphite composite material was prepared by the sol-gel technique and used for the fabrication of an amperometric nitrite sensor. The silicomolybdic anion acts as a catalyst, the graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. Cyclic voltammetry, square-wave voltammetry and chronoamperometry were employed to characterize the sensor. The amperometric nitrite sensor exhibited a series of good properties: high sensitivity (1.771 mu A mmol(-1) dm(3)), a short response time (7 s), remarkable long-term stability and especially reproducibility of surface renewal in the event of electrode surface fouling.

A new kind of potassium sensor based on capacitance measurement of mimic membrane

A novel type of potassium sensor based on the capacitance change of valinomycin-incorporated bilayer supported on a gold electrode has been developed and characterized. The lipid membrane was Formed by painted method and monitored simultaneously by capacitance variation. The capacitance of the electrode-supported membrane was found to be modulated by different concentrations of K+. Investigating the capacitance change allows a simple and specific technique for the measurement of potassium ion in solution. Especially, the homemade capacitance meter is, to our knowledge, used to monitor the bilayer membrane formation and detect K+ for the first time. It has been proved that this capacitance measurement is a very useful technique because it is simple and sensitive compared to the other methods.

Ion channel sensor

The ion channel sensor is reviewed. The concept and sensing principle of this kind of sensor are briefly discussed. The fabrication of the sensing membrane and the application of the ion channel sensor in electroanalytical chemistry are evaluated. The future developing direction is also anticipated.

Studies on the fusion heat of poly(ether ether ketone ketone)-poly(ether biphenyl ether ketone ketone) copolymers

On the basis of DSC measurements, the Delta H-f(0) values of the fusion heat for PEEKK-PEBEKK copolymers with various biphenyl contents were obtained by using thermodynamics statistical theory proposed by Flory and graphical method of the specific volume-fusion heat. The results reveal that Delta H-f(0) values determined by these two methods for PEEKK-PEBEKK copolymers with various biphenyl content are nearly the same, and that Delta H-f(0) values are closely dependent on biphenyl content. Delta H-f(0) value is minimum at n(B)=0.35.

CHOLESTEROL SENSOR-BASED ON ELECTRODEPOSITION OF CATALYTIC PALLADIUM PARTICLES

A layer of palladium particles was electrodeposited on a glassy carbon electrode. The dispersed Pd particles resulted in a large decrease in overvoltage for the electrochemical oxidation of H2O2 down to +0.4 V vs. Ag/AgCl, based on which a new kind of cholesterol sensor was fabricated. Cholesterol oxidase was immobilized on the Pd-dispersed electrode by cross-linking with glutaraldehyde and a layer of poly(o-phenylenediamine) (PPD) film was electropolymerized on the enzyme layer. The sensor shows a linear response in the concentration range 0.05-4.50 mmol l-1 with a rapid response of less than 20 s. The polymer film can prevent interference from uric acid and ascorbic acid and also increases the thermal stability of the sensor. The sensor can be used for 200 assays without an obvious decrease in activity.

FLOW-INJECTION ANALYSIS OF GLUCOSE AT AN AMPEROMETRIC GLUCOSE SENSOR-BASED ON ELECTROCHEMICAL CODEPOSITION OF PALLADIUM AND GLUCOSE-OXIDASE ON A GLASSY-CARBON ELECTRODE

A glassy carbon electrode (GCE) modified with palladium provides excellent electrocatalytic oxidation of hydrogen peroxide. When the electrolyte contains palladium chloride and glucose oxidase, the GCE can be modified by electrochemical codeposition at a given potential. The resulting modified surface was coated with a thin film of Nation to form a glucose sensor. Such a glucose sensor was successfully used in the flow-injection analysis of glucose with high stability and anti-poisoning ability. It gave a detection limit of 1 X 10(-7) M injected glucose, with a linear concentration range of 0.001-8 mM. There is no obvious interference from substances such as ascorbate and saccharides.

A NEW HYDROGEN SENSOR WITH RARE-EARTH COMPLEX FLUORIDE

A new type of solid-state galvanic cell for detecting a small amount of hydrogen in air at room temperature is proposed. The sensor cell is a potentiometric cell using Ce0.95Ca0.05F2.95 as solid-state electrolyte. The cell exhibits good sensing properties to hydrogen in air at room temperature.

AMPEROMETRIC GLUCOSE SENSOR WITH FERROCENE AS AN ELECTRON-TRANSFER MEDIATOR

A glucose oxidase (GOD) electrode with ferrocene (Fc) used as an electron transfer mediator has been described. Using Nafion, Fc was modified on a glassy carbon (GC) electrode surface, and glucose oxidase was then immobilized on the Fc-Nafion film, forming a GOD-Fc-Nafion enzyme electrode. The preparation method was quite simple and rapid. The enzyme electrode showed a reversible reaction of the redox couple (Fc+/Fc), used in a biosensor system, displayed a sensitive catalytic current response (response time was less than 20 s) on variation of the glucose concentration, with a wide linear range up to 16 mM and with good repeatability. The enzyme electrode showed almost no deterioration over the course of three weeks. There was little or no interference from electro-active anions, such as ascorbic acid, to the determination of glucose based on Nafion film and lower oxidizing potentials of the enzyme electrode.

A NEW KIND OF CONDUCTING POLYMER POLYPYRROLE (PPY) BR- ION CHEMICAL SENSOR

The modification of conducting polymer polypyrrole(PPy) on glassy carbon(GC)by electrcchemical technique, and the study on doping effect of Br anion and electrochemical behavior of PPy film electrode were reported.A new kind of Br~- ion selective electrode has been prepared successfully.The mechanism of the electrode potential response is based on the doping effect of anion in the conducting polymer.Effect of polymerization conditions on the potential response characteristic is investigated in dtail.The PPy...

An electrochemical DNA sensor based on electrodepositing aluminum ion films on stearic acid-modified carbon paste electrode and its application for the detection of specific sequences related to bar gene and CP4 Epsps gene

An electrochemical DNA biosensor was fabricated by immobilizing DNA probe on aluminum ion films that were electrodeposited on the surface of the stearic acid-modified carbon paste electrode (CPE). DNA immobilization and hybridization were characterized with cyclic voltammetry (CV) by using methylene blue (MB) as indicator. MB has a couple of well-defined voltammetric redox peaks at the CPE. The currents of redox peaks of MB decreased after depositing aluminum ion films on the CPE (Al(III)/CPE) and increased dramatically after immobilizing DNA probe (ssDNA/Al(III)/CPE). Hybridization of DNA probe led to a marked decrease of the peak currents of MB, which can be used to detect the target single-stranded DNA. The conditions for the preparation of Al(III)/CPE, and DNA immobilization and hybridization were optimized. The specific sequences related to bar transgene in the transgenic corn and the PCR amplification of CP4 epsps gene from the sample of transgenic roundup ready soybean were detected by differential pulse voltammetry (DPV) with this new electrochemical DNA biosensor. The difference between the peak currents of MB at ssDNA/Al(III)/CPE and that at hybridization DNA modified electrode (dsDNA/Al(III)/CPE) was applied to determine the Specific sequence related to the target bar gene with the dynamic range comprised between 1.0 X 10(-7) mol/L to 1.0 x 10(-4) mol/L. A detection limit of 2.25 x.10(-8) mol/L. of oligonucleotides can be estimated.

Lineage-specific domain fusion in the evolution of purine nucleotide cyclases in cyanobacteria

Cyclic nucleotides (both cAMP and cGMP) play extremely important roles in cyanobacteria, such as regulating heterocyst formation, respiration, or gliding. Catalyzing the formation of cAMP and cGMP from ATP and GTP is a group of functionally important enzymes named adenylate cyclases and guanylate cyclases, respectively. To understand their evolutionary patterns, in this study, we presented a systematic analysis of all the cyclases in cyanobacterial genomes. We found that different cyanobacteria had various numbers of cyclases in view of their remarkable diversities in genome size and physiology. Most of these cyclases exhibited distinct domain architectures, which implies the versatile functions of cyanobacterial cyclases. Mapping the whole set of cyclase domain architectures from diverse prokaryotic organisms to their phylogenetic tree and detailed phylogenetic analysis of cyclase catalytic domains revealed that lineage-specific domain recruitment appeared to be the most prevailing pattern contributing to the great variability of cyanobacterial cyclase domain architectures. However, other scenarios, such as gene duplication, also occurred during the evolution of cyanobacterial cyclases. Sequence divergence seemed to contribute to the origin of putative guanylate cyclases which were found only in cyanobacteria. In conclusion, the comprehensive survey of cyclases in cyanobacteria provides novel insight into their potential evolutionary mechanisms and further functional implications.

Assessing the potential of VEGETATION sensor data for mapping snow and ice cover: a Normalized Difference Snow and Ice Index

The VEGETATION (VGT) sensor in SPOT 4 has four spectral bands that are equivalent to Landsat Thematic Mapper (TM) bands (blue, red, near-infrared and mid-infrared spectral bands) and provides daily images of the global land surface at a 1-km spatial resolution. We propose a new index for identifying and mapping of snow ice cover, namely the Normalized Difference Snow/Ice Index (NDSII), which uses reflectance values of red and mid-infrared spectral bands of Landsat TM and VGT. For Landsat TM data, NDSII is calculated as NDSIITM =(TM3 -TM5)/(TM3 +TM5); for VGT data, NDSII is calculated as NDSIIVGT =(B2- MIR)/(B2 + MIR). As a case study we used a Landsat TM image that covers the eastern part of the Qilian mountain range in the Qinghai-Xizang (Tibetan) plateau of China. NDSIITM gave similar estimates of the area and spatial distribution of snow/ice cover to the Normalized Difference Snow Index (NDSI=(TM2-TM5)/(TM2+TM5)) which has been proposed by Hall et al. The results indicated that the VGT sensor might have the potential for operational monitoring and mapping of snow/ice cover from regional to global scales, when using NDSIIVGT.

一种高效覆盖的水下传感器网络部署策略

传感器节点的部署直接关系到水下传感器网络的成本和性能。考虑到传感器节点间具有很强的协同能力,该文提出一种基于检测融合的部署策略。采用Neyman-Pearson准则融合单元网格内所有传感器节点的检测信息,实现正方形和正三角形两种单元网格的高效覆盖,进而分别给出针对两种单元网格的监测区域网格划分方法,从而确定监测区域需要的传感器节点数量以及放置的具体位置。通过仿真实验验证了该部署策略的有效性。结果表明,与不采用检测融合时相比,降低了传感器节点冗余度。使用相同数量的传感器节点,新的部署策略能够在保证一定感知质量的基础之上获得更大的覆盖范围。

基于多传感器融合的组合导航方法研究

本文提出一种基于多传感器融合的组合导航方法,能够在小型旋翼无人机上实现低成本、高精度导航定位.该方法通过建立导航系统的机械编排模型,设计了一个17状态的扩展卡尔曼滤波器(EKF).对加速计的零偏和陀螺仪的漂移进行在线估计,实时的补偿传感器的测量误差.从而对旋翼无人机的速度、位置、角速度和姿态等参数进行精确的估计.通过对实际飞行数据仿真实验,并对比参考的导航系统,证明该方法在飞机的全包线飞行下均能够解算出可靠的导航信息。

基于多传感器的可变形机器人自主控制方法研究

将GPS、电子罗盘、倾角仪、码盘传感器等应用到可变形机器人自主运动控制中.针对可变形机器人自身结构特点,提出了一种基于多传感器信息融合的可变形机器人在野外环境中自主控制的方法.该方法主要实现了在非结构环境中机器人的自主变形、自主避障和自主导航定位等功能.实验验证了该方法的有效性.