Antiplane time-harmonic green’s functions for a circular inhomogeneity with an imperfect interface

Two-dimensional antiplane time-harmonic Green’s functions for a circular inhomogeneity with an imperfect interface are derived. Here the linear spring model with vanishing thickness is employed to characterize the imperfect interface. Explicit expressions for the displacement and the stress fields induced by time-harmonic antiplane line forces located both in the unbounded matrix and in the circular inhomogeneity are presented. When the circular frequency approaches zero, our results reduce to those for the static case. Numerical results are presented to show the influence of the frequency and the imperfection of the interface on the stress and displacement fields.     

Fiber Optical Bragg Grating Refractometer

We have demonstrated an evanescent field refractive indexfiber sensor comprising a 42-mm Bragg grating in an etched fiber together with a tunable Distributed Bragg Reflector (DBR) laser. Characterization of different aqueous sucrose solutions resulted in a resolution of roughly 10 mM sucrose. The sensor in the presented form has a theoretical sensitivity of higher than 10 5 refractive index unit (riu) in a refractive index region close to the cladding index of the fiber. However, the technique allows for an even higher sensitivity than 10 6 riu with a proper signal processing scheme.     

Superpositioned dielectrophoresis for enhanced trapping efficiency

One of the major applications for dielectrophoresis is selective trapping and fractionation of particles. If the surrounding medium is of low conductivity, the trapping force is high, but if the conductivity increases, the attraction decreases and may even become negative. However, high-conductivity media are essential when working with biological material such as living cells. In this paper, some basic calculations have been performed, and a model has been developed which employs both positive and negative dielectrophoresis in a channel with interdigitated electrodes. The finite element method was utilized to predict the trajectories of Escherichia coli bacteria in the superpositioned electrical fields. It is shown that a drastic improvement of trapping efficiency can be obtained in this way, when a high conductivity medium is employed.     

纳米TiO2的光生电荷迁移特性研究

利用场诱导光电压谱(简称FISPS)和瞬态光伏(简称TPV)技术研究了TiO₂的光生电荷的产生和传输机制.发现光生电荷在体块TiO₂上的迁移机制不同于在纳米TiO₂上的迁移机制，也不同于在结界面空间电荷区的迁移机制. 400 ℃处理的TiO₂颗粒表面具有大量的表面态，光生电荷被表面态捕获-释放机制控制着光伏行为的过程是慢过程. 800 ℃处理的TiO₂已经形成了完整的能带结构，光伏响应除了表现带-带跃迁外,还有一个在带边的自由激子带，光生电荷被表面自建场驱动进行传递的过程是快过程. 600 ℃处理的TiO₂混晶由锐钛矿型和金红石型两种构型组成，在两相之间存在着较低势垒的结界面．它的光伏响应受控于两种机制 ：光生电荷在两相间结界面空间电荷区的传输和在表面自建场驱动下的传输.当激发光强较小时，界面空间电荷区的光生电子由于积累的浓度较小而不能隧穿过结界面，这种场助隧穿只有在外场作用下才能发生.     

Nanowire‐Based Electrochemical Biosensors

We review recent advances in biosensors based on one‐dimensional (1‐D) nanostructure field‐effect transistors (FET). Specifically, we address the fabrication, functionalization, assembly/alignment and sensing applications of FET based on carbon nanotubes, silicon nanowires and conducting polymer nanowires. The advantages and disadvantages of various fabrication, functionalization, and assembling procedures of these nanosensors are reviewed and discussed. We evaluate how they have been used for detection of various biological molecules and how such devices have enabled the achievement of high sensitivity and selectivity with low detection limits. Finally, we conclude by highlighting some of the challenges researchers face in the 1‐D nanostructures research arena and also predict the direction toward which future research in this area might be directed.     

离子敏感场效应晶体管及其应用

离子敏感场效应晶体管具有若干不同于寻常传感器的特点：超小型、全固态、集成化和自身阻抗变换等。它是一种很有发展前途的传感器。本文了讨论了离子敏感场效应晶体管的分类、结构和性能；评述了１９８９年以来其在临床医学和流动注射分析等方面的应用。引参考文献６７篇。     

Vibronic intensities in centrosymmetric lanthanide complex ions. I

Summary A theoretical model to calculate the vibronic intensities induced by the odd vibrational modes in centrosymmetric lanthanide complexes is developed and applied to octahedral complex ions, LnX ₆ ^3– , such as occur in the hexachloroelpasolites Cs₂NaLnCl₆. Both the crystal field and the ligand polarisation contributions are evaluated using a standard set of symmetry coordinates. For the crystal field term a truncated expansion of the intermediates states is employed rather than the more conventional closure approximation. Special care is necessary to ensure that the phases of the contributions are correctly determined since the cross-term between the ligand polarisation and crystal field contributions is signed. General equations applicable to anyf ⁿ complex ion are derived and an example of their application to the PrCl ₆ ^3– ion is given The agreement with experiment is satisfactory.     

A new imidazolylquinoline for organic thin film transistor

A new active electronic material, 2-(naphtho[3,4]imidazol-2-yl)quinoline (NIQ), 1, has been synthesized and fully characterized. This compound exhibits field-effect carrier mobility and behaves as a p-type semiconductor (μ_FET = 0.148 cm²/V s at V_DS = 10 V). NIQ and its related imidazolylquinoline compounds may have possible applications as active materials in organic thin film transistors.     

Selective spectrophotometric determination of TNT in soil and water with dicyclohexylamine extraction

Contaminated land and groundwater remediation in military waste dumping sites often necessitates the use of simple, cost-effective, and rapid tests for detecting trinitrotoluene (TNT) residues in the field along with their dinitro-analogues. A simple, rapid, low-cost, and field-adaptable (on-site) colorimetric method was developed for quantifying TNT in the presence of RDX, PETN, picric acid, 2,4-DNT (dinitrotoluene), dinitrophenol, and dinitroaniline. Most commercialized methods for TNT assay-with the exception of Cold Regions Research and Engineering Laboratory of the U.S. Army (CRREL) method-use proprietary chemicals, and the color stability and intensity are highly dependent on the composition of the organic solution comprised of acetone or methanol. The developed colorimetric method is based on the extraction of TNT from water-acetone solution into an organic solvent mixture of dicyclohexylamine (DCHA)-isobutyl methyl ketone (IBMK) (10:1, v/v), filtration through a filter paper into a stoppered optical cell containing anhydrous sodium sulfate, and measurement of the absorbance of the organic extract at 531 nm after 5 min. The red-violet color of the extract was due to intermolecular charge-transfer (CT) between the electron attracting TNT and electron-donating DCHA, and the molar absorptivity for TNT in final organic solution was (1.16 ± 0.02) × 10⁴ L mol⁻¹ cm⁻¹.The R.S.D. of the slope of calibration line was 0.7%. The LOD of the method in the final organic phase was 0.38 μM TNT, and LOD values expressed on the basis of original soil TNT content were 0.5, 1.3, and 1.5 ppm (μg g⁻¹) for clay, loamy clay, and sandy soils, respectively. Unlike other spectrophotometric methods, the developed assay was basically tolerant to common cations and anions found in soil and water at 100-fold weight ratios, and to soil humic acids. Among a number of compounds that may be encountered in polynitro-explosive storage and waste reclaimation sites such as picric acid, dinitrophenol, 2,4-dinitrotoluene, dinitroaniline, RDX, PETN, and tetryl, only tetryl interfered with the developed TNT assay. Water tolerance and exploitability over a wide pH range were other superiorities over the CRREL method. The CT-complex was relatively stable, as the absorbance of the organic extract was not significantly influenced from the dilution of the water-acetone phase. Aside from the extractive-photometric procedure established for aqueous solutions, a simulated field colorimetric assay for TNT directly applicable to soil was also devised, based on direct color development in a 4:1 (v/v) acetone-dicyclohexylamine organic extract of soil at a liquid-to-solid ratio of 5 mL g⁻¹.     

Development and validation of a capillary electrophoresis method for the determination of phenothiazines in human urine in the low nanogram per milliliter concentration range using field-amplified sample injection

A capillary zone electrophoresis (CZE) method with ultraviolet-visible detection has been established and validated for the determination of five phenothiazines: thiazinamium methylsulfate, promazine hydrochloride, chlorpromazine hydrochloride, thioridazine hydrochloride, and promethazine hydrochloride in human urine. Optimum separation was obtained on a 64.5 cm x 75 microm bubble cell capillary using a buffer containing 150 mM tris(hydroxymethyl)aminomethane and 25% acetonitrile at pH 8.2, with temperature and voltage of 25 degrees C and 20 kV, respectively. Naphazoline hydrochloride was used as an internal standard. Field-amplified sample injection (FASI) has been applied to improve the sensitivity of the detection. Considering the influence of parameters affecting the on-line preconcentration (nature of preinjection plug, sample solvent composition, injection times, and injection voltage) and due to the significant interactions among them, in this paper we propose for the first time the application of a multivariate approach to carry out the study. The optimized conditions were as follows: preinjection plug of water for 7 s at 50 mbar, electrokinetic injection for 40 s at 6.2 kV, and 32 microm of H3PO4 in the sample solvent. Also, a solid-phase extraction (SPE) procedure is developed to obtain low detection limits and an adequate selectivity for urine samples. The combination of SPE and FASI-CZE-UV allows adequate linearities and recoveries, low detection limits (from 2 to 5 ng/mL), and satisfactory precisions (3.0-7.2% for an intermediate RSD %).