Tb_1-_xDy_x(Fe_1-_yMn_y)_(1.95)合金的磁致伸缩和声学性质及在水声换能器中的应用

研究了Ｔｂ１－ｘＤｙｘ（Ｆｅ１－ｙＭｎｙ）１．９５合金的磁致伸缩、声学等性质及其在水声换能器中的应用。当外加的磁场强度≥８００ｋＡ·ｍ－１时,磁致伸缩系数值在（１３００～１８００）×１０－６范围,有效机电偶合系数值０８４～０９３,声速为２１６８～２８５６ｍ·ｓ－１,杨氏模量为（５０６～７２６）×１０１０Ｎ·ｍ－２;用合金棒材研制水声换能器,该换能器总长３００ｍｍ,总重２ｋｇ,其共振频率为２４ｋＨｚ,发射电流响应１７３ｄＢ,频宽１ｋＨｚ,电声效率４５％     

Color-specific conditioning effects due to both orange and blue stimuli are observed in a Halobacterium salinarum strain devoid of putative methylatable sites on HtrI

Behavioral responses of Halobacterium salinarum appear as changes in the frequency of motion reversals. Turning on orange light decreases the reversal frequency, whereas blue light induces reversals. Light pulses normally induce the same response as step-up stimuli. However, anomalous behavioral reactions, including inverse responses, are seen when stimuli are applied in sequence. The occurrence of a prior stimulus is conditioning for successive stimulation on a time scale of the same order of adaptational processes. These prolonged conditioning effects are color-specific. The only adaptation process identified so far is methylation of the transducers, and this could be somehow color-specific. Therefore we tested for the behavioral anomalies in a mutant in which all methylation sites on the transducer have been eliminated. The results show that behavioral anomalies are unaffected by the absence of methylation processes on the transducer.     

Optimised layer systems for immunosensors based on the RIFS transducer

Several approaches to direct affinity sensing are currently under investigation. Prominent approaches based on optical transducers are surface plasmon resonance (SPR), grating couplers and interferometers. In this paper, investigations on the reflectometric interference spectroscopy (RIFS), a transducer based on thin dielectric films, are presented and discussed. The main advantages of the RIFS transducer are its ruggedness, the small active area and simple construction. However limits of detection so far achieved are only in the medium range. One way to improve detection is to increase the signal-to-noise ratio (s/n) in the primary signal (i.e. the reflectance spectra of the transducing film). The influence of the s/n-parameter was investigated by systematic variation of measurement parameters in a given system. A linear relationship between baseline noise of the transducer and s/n ratio of the primary signal was found with an offset value of about 1 pm rms. As the s/n value in the primary signal depends strongly on the optical properties of the transducing layer system, several single and two layer systems have been investigated for theoretical and experimental performance. An up to five-fold increase in signal intensity was achieved as compared to conventional single layer systems. In addition the improved layer systems can be prepared on low refractive index substrates (float glass), producing disposable transducers and giving improved optical systems. The experimental results indicate a thickness resolution of as low as 1 pm rms corresponding to protein coverages below 10 pg/mm². In applications where only moderate detectivity is required, these results offer the possibility for further miniaturisation of the device.     

Enzyme-free amperometric sensing of glucose by using gold nanoparticles

A nonenzymatic electrochemical method is described for the detection of glucose by using gold (Au) nanoparticles self-assembled on a three-dimensional (3D) silicate network obtained by using sol-gel processes. The nanosized Au particles have been self-assembled on the thiol tail groups of the silicate network and enlarged by hydroxylamine. The Au nanoparticles efficiently catalyze the oxidation of glucose at less-positive potential (0.16 V) in phosphate buffer solution (pH 9.2) in the absence of any enzymes or redox mediators. The Au nanoparticle-modified transducer (MPTS-nAuE) was successfully used for the amperometric sensing of glucose and it showed excellent sensitivity with a detection limit of 50 nM. The common interfering agent ascorbate (AA) does not interfere with the detection of glucose. The MPTS-nAuE transducer showed individual voltammetric responses for glucose and AA. This transducer responded linearly to glucose in the range of 0-8 mM and the sensitivity of the transducer was found to be 0.179 nA cm(-2) nM(-1). Excellent reproducibility, and long-term storage and operational stability was observed for this transducer.     

Development of an assay for label-free high-throughput screening of thrombin inhibitors by use of reflectometric interference spectroscopy

We describe the development of, and analytical conditions used for, parallel affinity assay for thrombin inhibitors adapted to the first label-free optical screening HTS detection set-up fully integrable into a screening platform. To achieve compatibility with pharmaceutical libraries, an HTS-transducer was realized by gluing the bottomless scaffolds of 96- and 384-well plastic microplates on to transducer slides. The transducer are coated with a dextran, to ensure biocompatibility and functionality, and a known thrombin inhibitor was attached covalently to it. By adapting reflectometric interference spectroscopy for simultaneous reading of the whole transducer plate we were able to detect the binding of thrombin in all the wells of the microplates on-line, in parallel, and time resolved. By using an inhibition assay, the screening of 384 substances for thrombin activity can be performed within an assay time of less than 15 min. We also show that the data quality is high enough for parallel quantification of the IC 50 values of the library substances.     

平面波导型荧光免疫传感器的制备与应用

研究了一种基于全内反射荧光和免疫检测原理的传感器系统,它可用于检测水环境中的有机污染物,如2,4-D、藻毒素等.本系统采用长波长的荧光染料Cy 5.5,以氦氖激光器作为激发光源,结合流动注射分析系统,能够快速方便地对传感基片上发生的免疫反应进行测定.本研究介绍了平面波导型荧光免疫传感器的检测原理、系统结构设计、传感基片的修饰、小分子配基的固定和系统测试结果.实验结果表明,系统具有很高的稳定性,对荧光染料的响应灵敏度可达1nmol/L;修饰后的传感基片基本不对蛋白产生非特异性吸附,而对不同浓度小分子配基抗体的响应符合Logistic方程;传感基片重复使用20个周期后,性能没有明显的下降.     

Characterization of modified lead titanate piezoceramics. Application to the design of array transducers

Due to their high electromechanical anisotropy, lead titanate piezoelectric ceramics of modified composition are very interesting for designing either linear or annular ultrasonic transducer arrays used in medical diagnosis and in non-destructive testing. In this paper results of the characterization of three varieties of this type of material are presented. The characterization includes the measurement of the resonance frequency dispersion diagram of thin parallelepipedic elements and the measurement of the characteristics in the longitudinal thickness mode and the planar mode. In view of the application to the design of transducers, several types of structures are presented.     

Micro-chemical sensors based on fiber-optic excitation of surface plasmons

In this paper the theoretical base and experimental results of a new class of fiber optical supported surface plasmon resonance spectroscopy (SPRS) transducer is given. Surface plasmons were excited by polychromatic light, and the resonant excitation is detected as an intensity minimum in the measured spectra at certain wavelengths. The excitation takes place at the end zone of a multimode fiber coated with a thin surface plasmon resonance supporting metal layer. As examples for the large application field of this transducer a fiber optical immunosensor for the detection of antibodies against bovine serum albumin and a gas sensor for remote detection of tetrachloroethene was constructed and tested successfully. The sensors were constructed following the theoretical predictions for an optimal performance.     

基于碳纳米管/Ag/MoS2转导层的全固态钙离子选择电极

构建了一种电势稳定性好的全固态钙离子选择电极(Ca²⁺-ISE),采用碳纳米管(CNT)/Ag/MoS₂为转导层,自制的三脚架化合物作为钙离子载体,制备固体接触式Ca²⁺-ISE。 系统分析了全固态Ca²⁺-ISE的稳定性、能斯特斜率、响应范围、选择性系数等主要性能,发现制备的固体接触式Ca²⁺-ISE在钙离子浓度为1×10^-6~1×10^-1 mol/L范围内呈现线性能斯特响应,响应斜率为28.1 mV/decade。 CNT/Ag/MoS₂的引入有利于提高固体接触式Ca²⁺-ISE的离子浓度线性响应范围,缩短电势平衡时间,降低测试能斯特斜率与理论值差,对于Ca²⁺-ISE的长期在线检测有重要研究意义。     

Enhancing the Efficiency of Anodic Stripping Voltammetry in Systems Permitting a Change of the Solution without Opening the Circuit

A new design for a transducer for voltammetric stripping analysis was proposed. It allows electroaccumulation and electrostripping stages to be carried out in the solutions of different compositions without opening a circuit. The potentialities of the transducer were demonstrated in the analysis of samples containing complex salt and organic matrices without their preliminary mineralization.     

Stationary Convective Diffusion and Nonlinear Effects in an Electrochemical Transducer

Dependences of limiting and difference currents of an electrochemical transducer with gauze electrodes on the velocity of stationary electrolyte flow are studied using a method of three-dimensional finite volumes. The main reason for nonlinearity of the difference current is the transfer of electrolyte ions from one anode–cathode pair to another. In a transducer with electrodes of parallel wires arranged in a checkerboard pattern the difference current nonlinearity may be reduced by forty and more times.     

A photometric detector based on a blue light-emitting diode

The suitability of blue light-emitting diodes as radiation sources in molecular absorption spectroscopy was evaluated. Electronic as well as spectral considerations are discussed. A transducer based on a blue light-emitting diode and a photodiode is described which yields direct absorbance readings by passing the photocurrent to an integrated circuit logarithmic converter. The performance of this device was tested for commonly used spectrophotometric procedures for Cr, Mn, Zn, Fe and Cl and compared with conventional molecular absorption spectroscopy. Also investigated was the application of the transducer as a detector in flow-injection analysis.     

Amperometric determination of pesticides using a biosensor based on a polishable graphie-epoxy biocomposite

The determination of organophosphorus and carbamate pesticides was carried out using an amperometric transducer based on a robust, polishable and easily mechinable biocomposite. The biocomposite material contains graphite powder, a non-conducting epoxy resin and acetylcholinesterase. The enzyme retains its bioactivity in the rigid epoxy-graphite matric. Measurements were carried out with acetylhiocholine as a substrate. Thiocholine produced by enzymatic hydrolysis was oxidized electrochemically at 70 mV (vs. Ag/AgCl in pH 7.0 buffered solution with 0.1 M phosphate and 0.1 m KCl). The decrease rate of substrate steady-state current after the addition of pesticide was used for evaluation. The method of construction allows for the repetitive use of the electrode. Simple polishing procedures are used to regenerate the bioactive transducer surface.     

Microfluidic droplet sorting with a high frequency ultrasound beam

This paper presents experimental results demonstrating the feasibility of high frequency ultrasonic sensing and sorting for screening single oleic acid (lipid or oil) droplets under continuous flow in a microfluidic channel. In these experiments, hydrodynamically focused lipid droplets of two different diameters (50 μm and 100 μm) are centered along the middle of the channel, which is filled with deionized (DI) water. A 30 MHz lithium niobate (LiNbO(3)) transducer, placed outside the channel, first transmits short sensing pulses to non-invasively determine the acoustic scattering properties of the individual droplets passing through the beam's focus. Integrated backscatter (IB) coefficients, utilized as a sorting criterion, are measured by analyzing the received echo signals from each droplet. When the IB values corresponding to 100 μm droplets are obtained, a custom-built LabVIEW panel commands the transducer to emit sinusoidal burst signals to commence the sorting operation. The number of droplets tested for the sorting is 139 for 50 μm droplets and 95 for 100 μm droplets. The sensing efficiencies are estimated to be 98.6% and 99.0%, respectively. The sorting is carried out by applying acoustic radiation forces to 100 μm droplets to direct them towards the upper sheath flow, thus separating them from the centered droplet flow. The sorting efficiencies are 99.3% for 50 μm droplets and 85.3% for 100 μm droplets. The results suggest that this proposed technique has the potential to be further developed into a cost-effective and efficient cell/microparticle sorting instrument.     

A biomimetic mass-flow transducer utilizing all-optofluidic generation of self-digitized, pulse code-modulated optical pulse trains

We present a new mass-flow transducer producing responses in the form of optical pulse trains that are encoded with information on the strength and position of the stimulus. We implemented the self-digitization and encoding capabilities all-optofluidically, without involving external electronics, by integrating one optical fiber cantilever with multiple polymer optical waveguides on a microfluidic platform. The transducer can also be configured to respond only to transitional stimuli. These features closely mimic the rate-coding, action potential labeling, and rapid adaptation processes observed in biological mechanoreceptors and allow multiple transducers to transmit signals over a single, shared channel. We fabricated the transducer using polymer-based soft-lithography techniques. Its characterization confirmed the stimulus strength-dependent generation of optical pulses and the feasibility of multiplexing 2(n-1) to 2(n) transducers using n waveguides.     

Effect of interferents present in the internal solution or in the conducting polymer transducer on the responses of ion-selective electrodes

The effect of interferents present on the opposite side of the Pb²⁺-selective membrane has been studied for both internal solution and all-solid-state sensors with a conducting polymer (CP) transducer. For interferents with moderate selectivity coefficients (sodium cations) present in the internal solution or in the CP transducer phase, super-Nernstian responses were obtained. For sensors containing strongly discriminated interferents (lithium ions), however, responses typical of conventional electrodes are observed, despite the low activity of primary ions on the opposite side of the membrane. This effect is attributed to hindered incorporation of interfering ions into the membrane, which also impairs the long term stability of the potential. Because of the relatively small absolute amounts of interferents in the transducer of all-solid-state sensors, their exchange for primary ions occurs quickly. Thus, transformation of the sensor to one with a micromolar detection limit and high potential stability is observed.      

Sensitive and selective DNA detection based on the combination of hairpin-type probe with endonuclease/GNP signal amplification using quartz-crystal-microbalance transduction

In order to develop a highly sensitive and selective piezoelectric transducer for the detection of DNA, the bio-recognizing probe is for the first time designed by introducing a hairpin structure and a recognition site for EcoRI into an oligonucleotide sequence and signal amplifiers are prepared by modifying gold nanoparticles (GNPs) with biomolecules, deepening the application and understanding of biomaterials. The piezoelectric transducer is prepared by immobilizing designed hairpin recognition probe onto the quartz-crystal-microbalance (QCM). In the absence of target DNA, the hairpin probe is removed from the QCM surface after exposure to endonuclease, inhibiting the subsequent signaling reaction. In contrast, introduction of target DNA can open the hairpin probe due to the probe/target hybridization, dissociating the cleavable double-stranded portion. In this case, even if being treated with endonuclease, the integrated hairpin probe is maintained. Subsequent introduction of GNPs modified with detection probes that can hybridize to the terminal sequence of hairpin probe results in a many-folds increase of the frequency response. Utilizing the proposed transduction scheme, the reliable target DNA detection can be accomplished. The detection limit of 2 pM and dynamic response range for target DNA from 2 to 300 pM are obtained. Furthermore, single-base mismatched DNAs can be easily identified. The developed proof-of-principle of a novel piezoelectric transduction scheme is expected to establish a potential platform for the disease-associated mutation analysis and DNA hybridization detection in biotechnology and medical diagnostics.     

Real time monitoring of accelerated chemical reactions by ultrasonication‐assisted spray ionization mass spectrometry

Ultrasonication has been used to accelerate chemical reactions. It would be ideal if ultrasonication‐assisted chemical reactions could be monitored by suitable detection tools such as mass spectrometry in real time. It would be helpful to clarify reaction intermediates/products and to have a better understanding of reaction mechanism. In this work, we developed a system for ultrasonication‐assisted spray ionization mass spectrometry (UASI–MS) with an ~1.7 MHz ultrasonic transducer to monitor chemical reactions in real time. We demonstrated that simply depositing a sample solution on the MHz‐based ultrasonic transducer, which was placed in front of the orifice of a mass spectrometer, the analyte signals can be readily detected by the mass spectrometer. Singly and multiply charged ions from small and large molecules, respectively, can be observed in the UASI mass spectra. Furthermore, the ultrasonic transducer used in the UASI setup accelerates the chemical reactions while being monitored via UASI–MS. The feasibility of using this approach for real‐time acceleration/monitoring of chemical reactions was demonstrated. The reactions of Girard T reagent and hydroxylamine with steroids were used as the model reactions. Upon the deposition of reactant solutions on the ultrasonic transducer, the intermediate/product ions are readily generated and instantaneously monitored using MS within 1 s. Additionally, we also showed the possibility of using this reactive UASI–MS approach to assist the confirmation of trace steroids from complex urine samples by monitoring the generation of the product ions. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterisation and optimisation of an immunoprobe for triazines

The characterisation and optimisation of an optical immunoassay with label free detection based on Reflectometric Interference Spectroscopy (RIfS) is presented. The immunoprobe is operated in a sequential scheme, where Fab-fragments react with analyte molecules in a first step. In a second step the optical transducer is used to quantify the amount of unoccupied Fab- fragments in the reaction mixture binding to the hapten-modified transducer surface. For optimisation of the test, the Fab-fragment concentration was varied between 2x10(-8) mol/l and 2.5x 10(-9) mol/l. Down to a concentration of 5x10(-9) mol/l a reduction in the limit of detection has been observed. At the lowest concentration investigated no further improvement has been found due to a reduced binding of the analyte and a strong decrease of antibody binding at the transducer surface. This finding could be explained by the thermodynamics of the antigen-antibody reaction and the performance of the optical transducer used. The limit of detection obtained is discussed with respect to thermodynamics, transducer characteristics and immunoprobe test format.     

Optical biosensors based on Prussian Blue films

Optical biosensing schemes based on enzymatically modified inorganic/organic transparent films predominately composed of Prussian Blue are demonstrated. The composite film, which is non-electrochemically deposited on a non-conducting support. is used as an optical transducer for flow-through biosensors based on hydrolases and oxidases. Urease and glucose oxidase are utilized as model enzymes. Action of the urea biosensor is based on optical pH sensitivity of Prussian Blue indicator. The glucose biosensor is acting as first-generation optical biosensor based on in situ generated Prussian White transducer for hydrogen peroxide. These simple, single-pass transmission optical biosensors exhibit sensitivity in the millimolar range of concentration. The biosensors are very stable owing to presence of a poly(pyrrolylbenzoic acid) network in the composite material. This organic polymer plays a dual role as a binding agent for inorganic material and as a functionalized support for strong covalent immobilization of enzyme molecules.