Dielectric response and its light-induced change in undoped alpha-Si : H films below 13 MHz

The low frequency (<13 MHz) dielectric response and its light-induced change in undoped a-Si:H were investigated in detail. The dielectric constant epsilon (the real part) in this range decreases with illumination time: following a stretched exponential law similar to that found for other light-induced changes. The saturation relative change was about 0.1-0.2 % for the measured samples. The change is fading away either after repeated illumination-annealing training or by aging at room temperature. The present results indicate some rearrangement of the whole Si network caused by light soaking.

Investigation on acceleration response of fiber optic mandrel hydrophone

The acceleration response of fiber optic mandrel hydrophone is studied based on the theory of elastic dynamics in this paper. For the first time the influence of the optical fiber on the acceleration response is taken into consideration. And the derivation of the radial deformation of the mandrel is presented in details. The acceleration response is evaluated both theoretically and experimentally and the results are in good agreement.

Multi-exponentially photoelectric response of bacteriorhodopsin

A thin oriented bacteriorhodopsin (bR) him is deposited on a stainless steel slide by use of the electrophoretic sedimentation method. A junction is made with electrolyte gels having a counterelectrode to construct a bR-based photoelectric detector;. The photoelectric response signal to a 10 ns laser pulse is measured. A theory on the photoelectric kinetics of bR is developed based on the concept of the charge displacement current and the bR photocycle rate equations. Comparison between the theoretical and experimental results proves that the bR photoelectric response to a short laser pulse is a multi-exponential process. The decay time constants and amplitudes of each, exponential component are obtained by data fitting.

TUNNELING ESCAPE TIME OF ELECTRONS THROUGH DOUBLE-BARRIER RESONANT-TUNNELING STRUCTURES

Tunneling escape of electrons from quantum wells (QWs) has systematically been studied in an arbitrarily multilayered heterostructures, both theoretically and experimentally. A wave packet method is developed to calculate the bias dependence of tunneling escape time (TET) in a three-barrier, two-well structure. Moreover, by considering the time variation of the band-edge profile in the escape transient, arising from the decay of injected electrons in QWs, we demonstrate that the actual escape time of certain amount of charge from QWs, instead of single electron, could be much longer than that for a single electron, say, by two orders of magnitude at resonance. The broadening of resonance may also be expected from the same mechanism before invoking various inhomogeneous and homogeneous broadening. To perform a close comparison between theory and experiment, we have developed a new method to measure TET by monitoring transient current response (TCR), stemming from tunneling escape of electrons out of QWs in a similar heterostructure. The time resolution achieved by this new method reaches to several tens ns, nearly three orders of magnitude faster than that by previous transient-capacitance spectroscopy (TCS). The measured TET shows an U-shaped, nonmonotonic dependence on bias, unambiguously indicating resonant tunneling escape of electrons from an emitter well through the DBRTS in the down-stream direction. The minimum value of TET obtained at resonance is accordance with charging effect and its time variation of injected electrons. A close comparison with the theory has been made to imply that the dynamic build-up of electrons in DBRTS might play an important role for a greatly suppressed tunneling escape rate in the vicinity of resonance.

STUDIES ON TUNNELING ESCAPE TIME OF ELECTRONS FROM A QUANTUM-WELL IN MULTILAYERED HETEROSTRUCTURES

By considering the time variation of band-edge profile arising from the decay of injected charge in quantum wells(QWs), we employ a wave packet method to verify that the actual escape time of certain amount of electrons from QWs could be much larger than that for a single electron. The theoretical result is also in agreement with our measurement of escape time, performed by using a newly developed method--transient current response.

Time-dependent density-functional calculations for optical spectra of Na-2 and Na-4 clusters

With the frame of the time-dependent local density approximation, an efficient description of the optical response of clusters has been used to study the photo-absorption cross section of Na-2 and Na-4 clusters. It is shown that our calculated results are in good agreement with the experiment. In addition, our calculated spectrum for the Na-4 cluster is in better agreement with experiment than the GW absorption spectrum.

Retrieval of Electron Return Time from High-order Harmonics Generated in a Mixture of He and Ne Gases

In terms of single-atom induced dipole moment by Lewenstein model, we present the macroscopic high-order harmonic generation from mixed He and Ne gases with different mixture ratios by solving three-dimensional Maxwell's equation of harmonic field. And then we show the validity of mixture formulation by Wagner et al. [Phys. Rev. A 76 (2007) 061403(R)] in macroscopic response level. Finally, using least squares fitting we retrieve the electron return time of short trajectory by formulation in Kanai et al. [Phys. Rev. Lett. 98 (2007) 153904] when the gas jet is put after the laser focus.

Development of functionalized terbium fluorescent nanoparticles for antibody labeling and time-resolved fluoroimmunoassay application

Silica-based functionalized terbium fluorescent nanoparticles were prepared, characterized and developed as a fluorescence probe for antibody labeling and time-resolved fluoroimmunoassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion containing a strongly fluorescent Tb3+ chelate. N,N.N-1,N-1-12,6-bis(3'-aminomethyl-1'-pyrazolyl)phenylpyridine] tetrakis(acetate)-Tb3+ (BPTA-Tb3+), Triton X-100, octanol, and cyclohexane by controlling copolymerization of tetraethyl orthosilicate (TEOS) and 3-[2-(2- aminoethylamino)-ethylamino]propyl-trimethoxysilane (AEPS) with ammonia water. The characterizations by transmission electron microscopy and fluorometric quantum methods show that the nanoparticles are spherical and uniform in size, 45 +/- 3 nm in diameter, strongly fluorescent with fluorescence yield of 10% and a long fluorescence lifetime of 2.0 ms. The amino groups directly introduced to the nanoparticle's surface by using AEPS in the preparation made the surface modification and bioconjugation of the nanoparticles easier. The nanoparticle-labeled anti-human alpha-fetoprotein antibody was prepared and used for time-resolved fluoroimmunoassay of (x-fetoprotein (AFP) in human serum samples. The assay response is linear from 0.10 ng ml(-1) to about 100 ng ml(-1) with the detection limit of 0.10 ng ml(-1). The coefficient variations (CVs) of the method are less than 9.0%. and the recoveries are in the range of 84-98% for human serum sample measurements. (C) 2004 Elsevier B.V. All rights reserved.

Concentration and time dependant behavior of chlorpromazine interaction with supported bilayer lipid membrane

The interaction of chlorpromazine (CPZ) with supported bilaver lipid (dipalmitoyphosphatidylcholine) membrane (s-BLM) on the glassy carbon electrode (GCE) was investigated using cyclic voltammetry and ac impedance spectroscopy. The experimental data, based on the voltammetric response of Ru(NH3)(6)(3+) associated with the oxidation of CPZ on the electrode, indicated that the interaction of CPZ with s-BLM was concentration and time dependant. The interaction between them could be divided into three stages by the concentration of CPZ: low, middle and high concentration. At the first stage, s-BLM was not affected by CPZ and the interaction was only a penetration of a small quantity of CPZ molecule into s-BLM. At the second stage, the defects formed in s-BLM due to the penetration of more CPZ molecule into s-BLM. At the last stage, a high CPZ:lipid ratio reached in s-BLM, resulting in the solubilization of s-BLM. The interaction time had different effect at three stages.

Amplified immunoassay of human IgG using real-time biomolecular interaction analysis (BIA) technology

An automated biomolecular interaction analysis instrument (BI-Acore) based on surface plasmon resonance (SPR) has been used to determine human immunoglobulin G (IgG) in real time. Polyclonal anti-human IgG antibody was covalently immobilized to a carboxymethyldextran modified gold film surface. The samples of human IgG prepared in HBS buffer were poured over the immobilized surface. The signal amplification antibody was applied to amplify the response signal. After each measurement, the surface was regenerated with 0.1 mol/L H3PO4. The assay was rapid, requiring only 30 min for antibody immobilization and 20 min for each subsequent process of immune binding, antibody amplification and regeneration. The antibody immobilized surface had good response to human IgG in the range of 0.12-60 nmol/L with a detection limit of 60 pmol/L. The same antibody immobilized surface could be used for more than 110 cycles of binding, amplification and regeneration. The results demonstrate that the sensitivity, specificity and reproducibility of amplified immunoassay using real-time BIA technology are satisfactory.

Layer-by-layer assembly of multilayer films composed of streptavidin and biotinylated antibody by real-time biomolecular interaction analysis

Layer-by-layer assembly of multilayer films of streptavidin and biotinylated antibody was completed on the streptavidin coated surface. Real-time biomolecular interaction analysis (BIA) based on surface plasmon resonance technique was used to monitor the multilayer assembly in solution continuously. The results indicate that the uniform multilayer film can be fabricated successfully based on the strong interaction between streptavidin and biotin. The mean surface mass concentration of each adsorption layer is 1. 32 ng/mm(2) for biotinylated antibody, 2. 93 ng/mm(2) for streptavidin, according to the correlation of SPR response with surface concentration.

The involvement of HSP22 from bay scallop Argopecten irradians in response to heavy metal stress

Heat shock protein 22 (HSP22) is an important member of small heat shock protein (sHSP) subfamily which plays a key role in the process of protecting cells, facilitating the folding of nascent peptides, and responding to stress. In the present study, the cDNA of HSP22 was cloned from Argopecten irradians (designated as AiHSP22) by rapid amplification cDNA end (RACE) based on the expressed sequence tags (ESTs). The full-length cDNA of AiHSP22 was of 1,112 bp, with an open reading frame of 588 bp encoding a polypeptide of 195 amino acids. The deduced amino acid sequence of AiHSP22 showed high similarity to previously identified HSP22s. The expression patterns of AiHSP22 mRNA in different tissues and in haemocytes of scallops exposed to Cd2+, Pb2+ or Cu2+ were investigated by real-time quantitative RT-PCR. The mRNA of AiHSP22 was constitutively expressed in all examined tissues, including haemocyte, muscle, kidney, gonad, gill and heart. The expression level in heart and muscle was higher than that in other tissues. The mRNA level of AiHSP22 in haemocytes was up-regulated after a 10 days exposure of scallops to Cu2+, Pb2+ and Cd2+. However, the expression of AiHSP22 did not increase linearly along with the rise of heavy metal concentration. Different concentrations of the same metal resulted in different effects on AiHSP22 expression. The sensitive response of AiHSP22 to Cu2+, Pb2+ and Cd2+ stress indicated that it could be developed as an indicator of exposure to heavy metals for the pollution monitoring programs in aquatic environment.

Comparative proteomic profiles of the hepatopancreas in Fenneropenaeus chinensis response to hypoxic stress

Hypoxia, as one suboptimal environmental condition, can affect the physiological state of shrimp during pond aquaculture. To better understand the mechanism of response to hypoxic stress in Chinese shrimp Fenneropenaeus chinensis, proteome research approach was utilized. Differentially expressed proteins of hepatopancreas in adult Chinese shrimp between the control and hypoxia-stressed groups were screened. By 2-DE analysis, 67 spots showed obvious changes after hypoxia. Using LC-ESI-MS/MS, 51 spots representing 33 proteins were identified including preamylase, arginine kinase, phosphopyruvate hydratase, citrate synthase, ATP synthase alpha subunit, chymotrypsin BI, chitinase, ferritin, C-type lectin receptors, transketolase, formylglutathione hydrolase, formyltetrahydrofolate dehydrogenase, aldehyde dehydrogenase, glutathione peroxidase, cytosolic manganese superoxide dismutase, protein disulfide isomerase, beta-actin, oncoprotem nm23, crustacyanin-Cl and so on. These proteins could be functionally classified into several groups such as proteins related to energy production, metabolism-related proteins, immune-related proteins, antioxidant proteins, chaperones, cytoskeleton proteins and ungrouped proteins. The transcription levels of ten selected genes encode the identified proteins were analyzed by real-time PCR at different sampling times of hypoxia. This study is the first analysis of differentially expressed proteins in the hepatopancreas of shrimp after hypoxia and provides a new insight for further study in hypoxic stress response of shrimp at the protein level.

Cloning of cytoplasmic heat shock protein 90 (FcHSP90) from Fenneropenaeus chinensis and its expression response to heat shock and hypoxia

Heat shock protein 90 (HSP90) works as a multi-functional chaperone and is involved in the regulation of many essential cellular pathways. In this study, we have identified a full-length complementary DNA (cDNA) of HSP90 (FcHSP90) from Chinese shrimp Fenneropenaeus chinensis. FcHSP90 full-length cDNA comprised 2,552 bp, including a 2,181-bp open reading frame encoding 726 amino acids. Both homology analyses using alignment with previously identified HSP90 and a phylogeny tree indicated that FcHSP90 was a cytoplasmic HSP90. Real-time reverse transcription polymerase chain reaction analysis revealed that FcHSP90 was ubiquitously expressed in all the examined tissues but with highest levels in ovary of F. chinensis. FcHSP90 mRNA levels were sensitively induced by heat shock (from 25A degrees C to 35A degrees C) and reached the maximum at 6 h during heat shock treatment. Under hypoxia conditions, FcHSP90 mRNA levels, in both hemocytes and gill, were induced at 2 h and depressed at 8 h during hypoxia stress. The assessment of FcHSP90 mRNA levels under heat shock and hypoxia stresses indicated that the transcription of FcHSP90 was very sensitive to heat shock and hypoxia, so we deduced that FcHSP90 might play very important roles for shrimp to cope with environmental stress.

The lysosome and lysozyme response in Chinese shrimp Fenneropenaeus chinensis to Vibrio anguillarum and laminarin stimulation

The effect of laminarin and Vibrio anguillarum on neutral red retention (NRR) time of lysosome and lysozyme activity in blood cells was investigated in Chinese shrimp, Fenneropenaeus chinensis. In addition the variation, of total haemocyte counts (THC) and differential haemocyte counts (DHC) were dtermined simultaneously The. results showed that the lysosome membrane stability was significantly elongated with the longest NRR time for 180 min at 3 h after lamianrin injection, (p<0.05). The lysozyme activity of haemocytes showed a moderate increase simultaneously. THC also increased and with a highest percentage of semi-granular cell counts at 3 h after laminarin injection. However, the NRR time sharply decreased with the shortest NRR time for 13 min at 1.5 h after V. anguillarum injection. Compared to the control group, the lysozyme activity obviously increased after injection, which was demonstrated at 1.5 h though the THC decreased. The percentage of hyaline cells increased obviously after V. anguillarum injection (p<0.05). The results suggested that the shrimp immune status could be evaluated by using lysosome membrane stability and lysozyme activity. (C) 2008 Elsevier B.V. All rights reserved.