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A novel poly(dimethylsiloxane) (PDMS) -based microchip for DNA separation through electrophoresis has been developed using a micro-electro-mechanical-system(MEMS) technology. Unlike previous hybrid PDMS microchip, one PDMS film is first created on glass support by pressing method in our microchip. Thus, increased band-broadening phenomena, arising from the material nonuniformity at the walls of microchannel, can be avoided in electrophoresis process. A low-viscosity hydroxypropylmethylcellulose-100 (HPMC-100) is used as the separation medium for fluorescent intercalator-labeled double-stranded DNA (dsDNA) fragments. Mannitol is introduced to PDMS-based microchip as a separation medium additive to enhance separation efficiency. At applied electric field strength of 150 V/cm, excellent separations of the PCR marker could be achieved with an effective separation distance of 25 mm. [ABSTRACT FROM AUTHOR]

A modified electrode, based on a hexadecane (C16)-coated glassy-carbon electrode (GCE) has been developed for the determination of parathion. The electrochemical behavior of parathion was investigated by cyclic voltammetry (CV). The peak potential and peak current were found to depend on the supporting electrolyte and the pH of the buffer solution. The reduction currents for parathion were proportional to parathion concentration over the range 8×10–8–2×10–5 mol L–1. The detection limit was 2×10–8 mol L–1 parathion for an accumulation time of 30 s. The effects of organic and inorganic species on the determination of parathion were also studied. A procedure was developed to extract parathion from spiked soil samples using a mixture of dichloromethane and acetone as the extraction solvent. The complete extraction and analytical procedure are simple, inexpensive and rapid. Parathion was determined in a soil sample by use of linear scan voltammetry (LSV). [ABSTRACT FROM AUTHOR]

Pulsed laser ablation epitaxial Strancky-Krastanow growth of self-organized complex oxide Ce:BaTiO3 quantum dots on MgO(lOO) substrates is demonstrated. Atomic force microscopy and X-ray diffraction are used to observe the structure and the growth process of the self-organized complex oxide quantum dots. The average dimension, height, and the density of self-organized complex oxide Ce:BaTiO3 quantum dots are given. The nonlinear refractive indexes of the wetting layer and the selforganized ordered quantum dots are determined by the single beam Z-scan method. The mechanisms of the nonlinear effect enhancement for these low-dimensional structure are discussed. [ABSTRACT FROM AUTHOR]

By using laser molecular beam epitaxy (L-MBE), atomic scale epitaxid growth of BaTiO3(BTO) thin films on SrTiO3 (STO) substrates is achieved. Measurements of reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy reveal that the BTO films are c-axis oriented single crystals with smooth surface. The multi-layer ferroelectric/superconducting heterostructures are also prepared and the ferroelectric properties of BTO films are studied. The results show that by using L-MBE technique, high quality BTO films and improved device performance can be obtained. [ABSTRACT FROM AUTHOR]

Using a standard photolithographical procedure, chemical wet etching and thermal diffusion bonding technology, a chemical analysis device for Capillary Electrophoresis(CE) has been microfabricated on a planar glass substrate with a cross-column geometry. The channels on the microchip substrate are about 50 µm deep and 150 µm wide. By employing amino acids derived from 2,4-DiNitroFluoroBenzen (DNFB) on CE chip channels, the sample manipulating system is studied based on the principle of electrodynamics. [ABSTRACT FROM AUTHOR]

An 1-(pyridylazo)-2-naphthol modified glassy carbon electrode has been investigated as sensor for the measurement of trace levels of Cd2+. Cd2+ is deposited on the surface of a PAN modified glassy carbon electrode at –1.10 V (vs. SCE) via forming Cd2+–PAN and subsequent reduction at the electrode. In the following step, Cd-PAN is oxidized, and voltammograms are recorded by scanning the potential in a positive direction. Calibration plots were found to be linear in the range 2 × 10–8 mol/L to 8 × 10–7 mol/L. The detection limit was 5 × 10–10 mol/L, and the coefficient of variation, determined on one single electrode at a concentration of 5 × 10–7 mol/L, was calculated to be 3.2% (n = 5). Using this new kind of modified electrode, trace levels of Cd(II) in water samples were determined; the average recovery was calculated to be 98.78%. [ABSTRACT FROM AUTHOR]

The theoretical and experimental results demonstrate, for the first time, that the enhancement of the reflected surface second harmonic generation on the rough GaAs-Al interface arises from the nonlinear resonant excitation of the harmonic surface polariton mode with s-polarized incident radiation. The experimental results agree quite well with the theoretical analysis. An optimum surface second harmonic enhancement of ∼three orders of magnitude has been obtained. [ABSTRACT FROM AUTHOR]

The observation of intervalence subband transitions induced third-order nonlinear effect in Si1-xGex/Si multiple quantum wells was reported. The dc Kerr in a symmetric quantum well, in which the linear-electro-optic effect is absent, was measured. The spectra of the absorption coefficient changes Δα under external field was obtained using experimental Fourier transform infrared absorption data. The resulting changes of refractive index due to quantum-confined Stark effect was obtained by Kramers–Kronig relations based on measured absorption data. Moreover, under both 45° incident angle and normal incidence, TE-active transition was excited and corresponding changes of refractive index under dc field was observed. The measured large changes of refractive index make Si1-xGex/Si multiple quantum wells quite attractive for potential application in electro-optic devices such as modulators and switches. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper, a home-made SPR analytical system and a denaturalized bovine serum albumin (dBSA) SPR chip were used to detect biotin based on the method of an inhibition immunoassay. The experimental was compared with a commercial protocol. The conditions of regeneration were optimized. The dBSA SPR chip was fabricated by a self-assembling method and the derivative of biotin was immobilized on the dBSA SPR chip by using a on-line mode. A commercial instrument and a dextran-SPR-chip (CM5) were used to implement the same experiments. Based on the experiments of immune reactions between biotin antibody and biotin derivative, the biotin antibody concentration was optimized at about 5 μg/mL in order to obtain highly sensitivity, which was used in the followed inhibition immunoassays. The lowest detection limit for biotin is 0.1 μg/mL with a detection range of 0.1-1000 μg/ml by using our home-made instrument and the dBSA-SPR-chip. The detection results of our instrument and dBSA SPR chip are comparable with the commercial protocol. Our home-made instrument and dBSA-SPR-chips can be also applied to detect other small molecules based on the indirect inhibition immunoassay. [ABSTRACT FROM AUTHOR]

This paper presents a homemade miniature surface plasmon resonance (SPR) system with automatic sample injection device which is able to work 24 hours unattended. The system with a volume of 48cm×25cm×28 cm was constructed with a red laser light source, a P-polarizer, a triangle glass prism, a linear CCD detector, gold sensor chips modified with BSA or colloidal gold, an automatic sample injection device with 20 sample locations. The system sensitivity and noise were tested through detecting different concentration of glycerol solutions with a group of refractive indices (RIs). Cortisol-BSA was fixed on the gold sensor chips modified with BSA or colloidal gold. A series concentration of cortisol (1, 10, 100, 1000 ng/ml) mixed with cortisol-specific monoclonal antibodies were detected by miniature SPR system. The performance of BSA and colloidal gold modified sensor chips were compared by calculating the standard curves and the kinetic curves of the cortisol detection. The results showed that the BSA sensor chip could get a better detection limit of cortisol sample while the colloidal gold sensor chip owed a higher stability and repeatability by regenerating the antibody surface. The research studied the performance of the homemade SPR system and the sensor chips which could be widely used in the protein measurement areas. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) biosensors are an extremely sensitive optical technique used to detect the changes in refractive index occurring at the sensor interface. Fluorescence involves the emission of light by a substance that has absorbed light or other electromagnetic radiation, and the parameters of the absorbed and emitted radiation are used to identify the presence and the amount of specific molecules in a specimen. SPR biosensors and fluorescence analysis are both effective methods for real-time detection. The combination of these technologies would improve the quantitative detection sensitivity of fluorescence analysis and the specificity of SPR detection. We designed and developed an SPR and fluorescence synchronous detection system. The SPR module was based on two kinds of modulation methods, and the fluorescence module was capable of switching between four wavelengths. The fluorescence microspheres and A549 cells of different concentration were both detected by the SPR and fluorescence method synchronously in real time. The fluorescent signal and the optical signal of the SPR were shown to correlate. The correlation coefficient for fluorescent microspheres detection reached up to 0.9866. The system could be used in cell analysis and molecule diagnosis in the future. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the polarization properties of valence intersubband transitions in a type of multiple quantum wells using Fourier infrared absorption spectra. Experimental details; Use of x-ray diffraction and Raman scattering spectrum in analyzing the composition of the silicon germanium alloy; Findings of the study.

We reported on an experimental investigation and theoretical analysis of pulse repetition rate (PRR) adjustable deep ultraviolet (DUV) picosecond (ps) radiation by second harmonic generation (SHG) in KBe2BO3F2 (KBBF) crystal. Third harmonic radiation at 355 nm of a ps Nd:YVO4 laser output with PRR of 200 kHz–1 MHz was employed as the pump source. The dependence of the 177.3 nm output power on the 355 nm pump power was measured at different PRRs, and the maximum 177.3 nm average output power of 695 μW was obtained at the PRR of 200 kHz. The measured data agreed well with the results of the ps KBBF SHG theoretical simulations. Using simulations, the pulse width and the spectral bandwidth of the generated radiation at 177.3 nm were estimated to be 5.88 ps and 7.84 pm, respectively. [ABSTRACT FROM AUTHOR]

Abstract: An improved portable photoionization detector (PID) was proposed in this manuscript. A novel structure named “nozzle” with a volume slightly less than the ionization chamber was positioned in the center of the chamber, dramatically reducing the ionization chamber volume and improving device sensitivity. An annular accelerating electrode was embedded in the nozzle groove to shield from vacuum ultraviolet (VUV) light radiation, decreasing background noises. Then the improved PID combined with a high separation efficiently micro gas chromatography (GC) column was used to construct a portable rapid GC system. The results indicated that the proposed PID in this study demonstrated an ultra low background noise (≤1×10−14 A) and a small baseline drift. Moreover, the proposed PID was characterized with a response time less than 30ms and a large linear range of 106. The proposed system was used to detect gas mixtures with a detection limit less than 5ppb. [Copyright &y& Elsevier]

Abstract: Many kinds of macromolecular compounds that comprise a series of branches around an inner core have been made and showed some promises as DNA- and drug-delivery systems. In this study, a method for peptide polymer design having macro-branched peptide structure was adapted and it was applied for plasmid DNA delivery for the first time; acryloyl chloride was used by introducing the double bond into the N-terminal of HIV-1 tat (47–57, YGRKKRRQRRR). After being cleaved from resin, it was transformed to a polymer which possesses a poly-propionyl core matrix with tat branches and was named polytat by radical polymerization. After further separation and purification by Sephadex G150, polytat P1, polytat P2 and polytat P3 were acquired and the average molecular weight of the different macromolecules are 240, 178 and 82 kDa. We found that all these compounds complexed with plasmid DNA and showed significant transfection capabilities in a variety of mammalian cell lines, but acrylyl-tat or tat alone showed no significant transfection capability. Further study showed that polytat could be applied for plasmid DNA delivery for cell lines even with serum by endocytosis-mediated pathways. [Copyright &y& Elsevier]