Effect of Asymmetric Potential and Gaussian Colored Noise on Stochastic Resonance

The phenomenon of stochastic resonance (SR) in a bistable nonlinear system is studied when the system is driven by the asymmetric potential and additive Gaussian colored noise. Using the unified colored noise approximation method, the additive Gaussian colored noise can be simplified to additive Gaussian white noise. The signal-to-noise ratio (SNR) is calculated according to the generalized two-state theory (shown in [H.S. Wio and S. Bouzat, Brazilian J.Phys. 29 (1999) 136]). We find that the SNR increases with the proximity of a to zero. In addition, the correlation time τ between the additive Gaussian colored noise is also an ingredient to improve SR. The shorter the correlation time τ between the Gaussian additive colored noise is, the higher of the peak value of SNR.     

色噪声对光学双稳态的影响

采用统一色噪声近似构建了由乘法色噪声驱动的纯吸收型光学双稳态状态方程,并分析了色噪声对光学双稳态的影响,将结果与白噪声驱动的光学双稳态进行比较.结果表明:当乘法噪声与加法噪声处在正关联时,增加乘法色噪声的自关联时间r,光学双稳性的区域显著变宽,即磁滞回线面积变大;当乘法噪声与加法噪声处在负关联时,只有乘法噪声较小时,改变乘法色噪声的自关联时间r,光学双稳态才发生改变;当乘法噪声的自相关时间等于零时,本文模型退化为乘法白噪声驱动的光学双稳性状态方程.     

Nanohole 3D-size tailoring through polystyrene bead combustion during thin film deposition

A novel approach is presented for nanohole 3D-size tailoring. The process starts with a monolayer of polystyrene (PS) beads spun coat on silicon wafer as a template. The holes can be directly prepared through combustion of PS beads by oxygen plasma during metal or oxide thin film deposition. The incoming particles are prevented from adhering on PS beads by H₂O and CO₂ generated from the combustion of the PS beads. The hole depth generally depends on the film thickness. The hole diameter can be tailored by the PS bead size, film deposition rate, and also the combustion speed of the PS beads. In this work, a series of holes with depth of 4-24 nm and diameter of 10-36 nm has been successfully prepared. The hole wall materials can be selected from metals such as Au or Pt and oxides such as SiO₂ or Al₂O₃. These templates could be suitable for the preparation and characterization of novel nanodevices based on single quantum dots or single molecules, and could be extended to the studies of a wide range of coating materials and substrates with controlled hole depth and diameters.     

Fluoride removal using lanthanum incorporated chitosan beads

Highly selective material based on naturally occurring biomaterial namely chitosan has been designed for the defluoridation of water. Lanthanum incorporated chitosan beads (LCB) were prepared using precipitation method. The synthesis was optimized by varying different synthesis parameters namely lanthanum loading, complexation and precipitation time, strength of ammonia solution used for precipitation, drying time, etc. Lanthanum incorporated chitosan beads were characterized using SEM, FTIR, XRD and EDX. Surface area of LCB was observed to be 2.76 m² g⁻¹. The equilibrium adsorption data fitted well to Langmuir adsorption isotherm and showing maximum fluoride adsorption capacity of 4.7 mg g⁻¹ with negligible lanthanum release. Kinetic study reveals that adsorption of fluoride is fast and follows pseudo-first-order kinetics. The effect of pH was also studied and the best efficiency was observed at pH 5. Presence of sulphate, nitrate and chloride marginally affected the removal efficiency, however drastic reduction in fluoride uptake was observed in the presence of carbonate and bicarbonate. Negative value of change in free energy (ΔG°) and positive value of change in entropy (ΔS°) suggest the adsorption of fluoride by LCB is feasible and spontaneous process. Positive value of change in enthalpy (ΔH°) suggests the process of fluoride adsorption is endothermic in nature. Regeneration study reveals that 1 M ammonium chloride solution appears to be the promising regeneration media showing 81.22% regeneration. The adsorption capacity of LCB was similar in fluoride-contaminated ground water collected from Dhar district of Madhya Pradesh, India, as compared to simulated water.     

Improvement of extraction capability of magnetic molecularly imprinted polymer beads in aqueous media via dual-phase solvent system

In this study, a novel and simple dual-phase solvent system for the improvement of extraction capability of magnetic molecularly imprinted polymer (MIP) beads in aqueous sample was proposed. The method integrated MIP extraction and micro-liquid-liquid extraction (micro-LLE) into only one step. A magnetic MIP beads using atrazine as template was synthesized, and was applied to aqueous media by adding micro-volume of n-hexane to form a co-extraction system. The magnetic MIP beads preferred to suspend in the organic phase, which shielded them from the disturbance of water molecule. The target analytes in the water sample was extracted into the organic phase by micro-LLE and then further bound to the solid-phase of magnetic MIP beads. The beads specificity was significantly improved with the imprinting efficiency of template increasing from 0.5 to 4.4, as compared with that in pure aqueous media. The extraction capacity, equilibration process and cross-selectivity of the MIP dual-phase solvent extraction system were investigated.The proposed method coupled with high-performance liquid chromatography was applied to the analysis of atrazine, simazine, propazine, simetryn, prometryne, ametryn and terbutryn in complicated sample such as tomato, strawberry juice and milk. The method is selective, sensitive and low organic solvent-consuming, and has potential to broaden the range of MIP application in biological and environmental sample.     

A flow cytometric assay technology based on quantum dots-encoded beads

A flow cytometric detecting technology based on quantum dots (QDs)-encoded beads has been described. Using this technology, several QDs-encoded beads with different code were identified effectively, and the target molecule (DNA sequence) in solution was also detected accurately by coupling to its complementary sequence probed on QDs-encoded beads through DNA hybridization assay. The resolution of this technology for encoded beads is resulted from two longer wavelength fluorescence identification signals (yellow and red fluorescent signals of QDs), and the third shorter wavelength fluorescence signal (green reporting signal of fluorescein isothiocyanate (FITC)) for the determination of reaction between probe and target. In experiment, because of QDs’ unique optical character, only one excitation light source was needed to excite the QDs and probe dye FITC synchronously comparing with other flow cytometric assay technology. The results show that this technology has present excellent repeatability and good accuracy. It will become a promising multiple assay platform in various application fields after further improvement.     

Stochastic resonance for a metapopulation system driven by multiplicative and additive colored noises

We investigate the stochastic resonance(SR) phenomenon induced by the periodic signal in a metapopulation system with colored noises. The analytical expression of signal-to-noise is derived in the adiabatic limit. By numerical calculation, the effects of the addictive noise intensity, the multiplicative noise intensity and two noise self-correlation times on SNR are respectively discussed. It shows that:(i) in the case that the addictive noise intensity M takes a small value, a SR phenomenon for the curve of SNR appears; however, when M takes a large value, SNR turns into a monotonic function on the multiplicative noise intensity Q.(ii) The resonance peaks in the plots of the multiplicative noise intensity Q versus its self-correlation time τ1 and the addictive noise intensity M versus its self-correlation time τ2 translate in parallel. Meanwhile, a parallel translation also appears in the plots of τ1 versus Q and τ2 versus M.(iii) The interactive effects between self-correlation times τ1 and τ2 are opposite.     

完全图中的正常染色的路和圈

令$K_{n}^{c}$表示$n$ 个顶点的边染色完全图.
令 $\Delta^{mon}
(K_{n}^{c})$表示$K^c_{n}$的顶点上关联的同种颜色的边的最大数目.
如果$K_{n}^{c}$中的一个圈（路）上相邻的边染不同颜色,则称它为正常染色的.
B. Bollob\'{a}s和P. Erd\"{o}s (1976) 提出了如下猜想：若 $\Delta^{{mon}}
(K_{n}^{c})<\lfloor \frac{n}{2} \rfloor$, 则$K_{n}^{c}$中含有一个正常染
色的Hamilton圈. 这个猜想至今还未被证明.我们研究了上述条件下的正常染色的路和圈.     

Development of a novel label-free amperometric immunosensor for the detection of okadaic acid

Okadaic acid (OA), a lipophilic phycotoxin is mainly produced by toxigenic dinoflagellates. The need to develop high performing methods for OA analysis able to improve the traditional ones is evident. In this work, a novel experimental methodology for label-free detection of OA was developed. Protein G magnetic beads (protein-G-MBs) modified gold electrode was used to immobilize anti-OA monoclonal antibody (anti-OA-MAb). Preliminary, colorimetric tests were performed in order to validate protein-G-MBs and anti-OA-MAb reaction. Electrochemical detection was carried out by differential pulse voltammetry in ferri/ferrocyanide solution. The limit of detection value obtained (0.5 μg L⁻¹) validated the developed electrochemical immunosensor as a promising tool for routine use. The matrix effect and the recovery rate were also assessed with real samples, showing a good percentage of recovery.