Theory of the transmission of metal strip gratings on a dielectric substrate application to submillimeter laser coupling

The advantages of supported metal strip gratings with respect to free-standing metal meshes are pointed out for applications as laser output couplers. A new, simple formula for the power transmission through the strip grating on a dielectric plate is derived from a line equivalent-circuit model. This formula is in good agreement with measurements performed on several samples, at different submillimeter wavelengths. An application to output couplers of far-infrared gas discharge lasers allows to improve the reliability of such lasers.x Unité associée au CNRS. U.A. 836.     

High-index contrast grating based broadband out-coupler on SOI

An efficient broadband out-coupler on silicon-on-insulator (SOI) with high-index contrast grating (HCG) is proposed. The presence of a silicon-air (high-index contrast) grating on the top silicon layer in SOI allows a strong interaction between the guided mode and the grating. The broadband design of the out-coupler is presented by optimising the various grating parameters. The design analysis and simulation of such an out-coupler is performed with finite difference method. Coupling efficiency of 54% is achieved over an ultra-wide wavelength range from 1500 nm to 1650 nm.     

A novel immunochromatographic assay based on a time-resolved chemiluminescence strategy for the multiplexed detection of ractopamine and clenbuterol

A novel multiplexed immunochromatographic assay (ICA) based on a time-resolved chemiluminescence (CL) strategy was developed for quantitative detection of β-agonists, by utilizing ractopamine (RAC) and clenbuterol (CLE) as the models. Different from conventional multiplexed ICA methods which usually require two or more test lines, this strategy was developed for detection of two β-agonists by using only one test line on the nitrocellulose membrane. In this study, horseradish peroxidase and alkaline phosphatase were used as the signal probes to label RAC antibody and CLE antibody, respectively. The two CL reactions with flash type and glow type kinetics characteristics were triggered simultaneously by injecting the coreactants, then the signals for RAC and CLE detections were recorded at 3 s and 300 s after coreactants injection, respectively. Owing to the utilization of CL detection, this protocol showed ideal sensitivity for quantitation. Under the optimal conditions, the detection limits for RAC and CLE were 0.17 ng mL⁻¹ and 0.067 ng mL⁻¹ (S/N = 3), respectively. The whole assay process can be accomplished within 20 min without complicated sample pretreatment. The proposed method was successfully applied for the detection of RAC and CLE in spiked swine urine. It opens up a new pathway for designing a low cost, time-efficiency and multiplexed strategy for rapid screening and field assay.     

双合金结合速凝工艺制备烧结NdFeB研究

采用速凝工艺制备了主相合金铸片,由其微观形貌分析可见,富Nd相呈薄层状均匀分布在主相晶界处。XRD分析表明铸带形成了明显的取向织构。使用普通熔炼方法熔炼几种不同成分的辅相合金。将主相合金与辅相合金配比,运用双合金法工艺制备出烧结NdFeB磁体。研究表明Pr替代Nd有利于提高磁体的剩磁。     

A visual strip sensor for determination of iron

A visual strip has been developed for sensing iron in different aqueous samples like natural water and fruit juices. The sensor has been synthesized by UV-radiation induced graft polymerization of acrylamide monomer in microporous poly(propylene) base. For physical immobilization of iron selective reagent, the in situ polymerization of acrylamide has been carried out in the presence of 1,10-phenanthroline. The loaded strip on interaction with Fe(II) in aqueous solution turned into orange red color and the intensity of the color was found to be directly proportional to the amount of Fe(II) in the aqueous sample. The minimal sensor response with naked eye was found for 50 ng mL⁻¹ of Fe in 15 min of interaction. However, as low as 20 ng mL⁻¹ Fe could be quantified using a spectrophotometer. The detection limit calculated using the 3s/S criteria, where ‘s’ is the standard deviation of the absorbance of blank reagent loaded strip and ‘S’ is the slope of the linear calibration plot, was 1.0 ng mL⁻¹. The strip was applied to measure Fe in a variety of samples such as ground water and fruit juices.     

Development of a one-step immunochromatographic strip test for the rapid detection of nevirapine (NVP), a commonly used antiretroviral drug for the treatment of HIV/AIDS

Currently, high-performance liquid chromatographic (HPLC) methods are mainly used to measure antiretroviral plasma concentrations in HIV-infected patients. Although the utility of routine therapeutic drug monitoring (TDM) as an additional tool to optimize long-term antiretroviral therapy is unclear, if TDM is to be widely used, the availability of simple, cheap and reliable methods for the measurement of antiretroviral drug levels are needed, particularly in resource-limited settings. In this study, an immunochromatograhic (IC) strip test to detect the presence of nevirapine (NVP) in body fluids has been developed. Antiserum to NVP was first raised in rabbits by immunization against NVP chemically conjugated with bovine serum albumin, and subsequently validated by Western immunoblotting and competitive indirect ELISA. The partially purified anti-NVP antibodies were conjugated with colloidal gold particles. The conjugation of the colloidal gold and polyclonal antibodies was monitored by UV-vis spectroscopy, while transmission electron microscopy images were used to characterize the particle size and shape of the conjugates. The resulting colloidal gold conjugates were used for the production of an IC strip test to detect nevirapine in human plasma. Preliminary assessment suggests no-cross reactivity of the NVP polyclonal antibodies but assessment of plasma samples from HIV-infected patients receiving HAART needs to be conducted. This assay could potentially be used for drug monitoring as part of the clinical care of HIV infected patients.     

Griffith crack moving in a piezoelectric strip

Summary  The dynamic problem of an impermeable crack of constant length 2a propagating along a piezoelectric ceramic strip is considered under the action of uniform anti-plane shear stress and uniform electric field. The integral transform technique is employed to reduce the mixed-boundary-value problem to a singular integral equation. For the case of a crack moving in the mid-plane, explicit analytic expressions for the electroelastic field and the field intensity factors are obtained, while for an eccentric crack moving along a piezoelectric strip, numerical results are determined via the Lobatto–Chebyshev collocation method for solving a resulting singular integral equation. The results reveal that the electric-displacement intensity factor is independent of the crack velocity, while other field intensity factors depend on the crack velocity when referred to the moving coordinate system. If the crack velocity vanishes, the present results reduce to those for a stationary crack in a piezoelectric strip. In contrast to the results for a stationary crack, applied stress gives rise to a singular electric field and applied electric field results in a singular stress for a moving crack in a piezoelectric strip. Received 14 August 2001; accepted for publication 24 September 2002 The author is indebted to the AAM Reviewers for their helpful suggestions for improving this paper. The work was supported by the National Natural Science Foundation of China under Grant 70272043.     

Third-Order Dispersion in Linearly Chirped Bragg Gratings and Its Compensation

When fiber optics' quadratic dispersion is compensated, the cubic dispersion determines the transmission quality in an optical link. Although the third-order dispersion coefficient is small in standard fiber optics at the third window, it is not in the linearly chirped grating used to the second-order dispersion equalization. The influence of the grating parameters on its third-order dispersion value is systematically studied and an efficient and low-cost device is proposed thatis numerically proven to cancel the global third-order dispersion that arises from the optical link.