Sample conditions to avoid pH distortion in RP‐LC

Band deformations might take place for acids and bases in preparative applications and adsorption studies where it is necessary to use overloaded injections. In this study, we focus on how deformations can be prevented without using highly concentrated buffers that may precipitate in the eluent. We have systematically investigated how the elution zones depend on which protolytic form the analyte has when it is dissolved. Basic and acidic model compounds are investigated using eluents with different pH values and the resulting elution profiles are compared when the analytes are dissolved in their protonated and deprotonated form, i.e., in uncharged form or as different kinds of salts. Depending on the analyte's protolytic form, a sample zone is created at the column inlet whose pH deviates, more or less, from the bulk eluent's. If the local adsorption strength in this sample zone is greater than the bulk eluent's, the elution profiles are compressed. Under opposite conditions, the eluted bands are more or less deformed and may even be split; completely different deformations can even take place for different kinds of salt combinations. Explanations of these, and other, effects, together with detailed guidelines for proper sample preparation to avoid peak deformations, are given.     

Highly sensitive and selective detection of biothiols using graphene oxide-based “molecular beacon”-like fluorescent probe

A fluorometric method for quantity analysis of biothiols was developed using a graphene oxide (GO)-based “molecular beacon”-like probe, which consisted of FITC labeled thymine (T)-rich single-stranded DNA (ssDNA), GO and Hg²⁺ ions. The labeled ssDNA containing T–T mismatches would self-hybridize to duplex in the presence of Hg²⁺, which can avoid its adsorption on GO and the fluorescence of this GO-based probe was recovered. The fluorescence of the probe quenched after the addition of biothiols such as glutathione (GSH) and cysteine (Cys) owing to thiol groups can selectively competitive ligation of Hg²⁺ ions with T–T mismatches. In the present work, the GO-based probe was used for the determination of GSH and Cys. Under the optimal conditions, a linear correlation was established between fluorescence intensity ratio I₀/I and the concentration of GSH in the range of 2.0 × 10⁻⁹–5.0 × 10⁻⁷ mol L⁻¹ with a detection limit of 1.0 × 10⁻⁹ mol L⁻¹. The linear range for Cys is from 5.0 × 10⁻⁹ to 4.5 × 10⁻⁷ mol L⁻¹ with a detection limit of 2.0 × 10⁻⁹ mol L⁻¹. The proposed method was applied to the determination of GSH in human serum and cell extract samples with satisfactory results.     

Variable step-size subband backward BSS algorithms for speech quality enhancement

This paper addresses the problem of the speech quality improvement using adaptive filtering algorithms. Recently in Djendi and Bendoumia (2014) [1], we have proposed a new two-channel backward algorithm for noise reduction and speech intelligibility enhancement. The main drawback of proposed two-channel subband algorithm is its poor performance when the number of subband is high. This inconvenience is well seen in the steady state regime values. The source of this problem is the fixed step-sizes of the cross-adaptive filtering algorithms that distort the speech signal when they are selected high and degrade the convergence speed behaviours when they are selected small. In this paper, we propose four modifications of this algorithm which allow improving both the convergence speed and the steady state values even in very noisy condition and a high number of subbands. To confirm the good performance of the four proposed variable-step-size SBBSS algorithms, we have carried out several simulations in various noisy environments. In these simulations, we have evaluated objective and subjective criteria as the system mismatch, the cepstral distance, the output signal-to-noise-ratio, and the mean opinion score (MOS) method to compare the four proposed variables step-size versions of the SBBSS algorithm with their original versions and with the two-channel fullband backward (2CFB) least mean square algorithm.     

单模双折射色散缓变光纤中拉曼散射与参量放大

根据斯托克斯波和反斯托克斯波所满足的耦合微分方程,考虑泵浦波是线偏振光,其偏振方向沿x轴,推导出了同偏振方向受激拉曼散射和参量放大同时作用下,斯托克斯波和反斯托克斯波的增益系数。研究了色散缓变光纤中增益随失配系数Δk2以及归一化距离z/L的变化关系。结果表明,当非线性系数γ=0时,增益随Δk2的变化情况在正常和反常色散区是完全对称的;而当非线性系数γ≠0时,在反常色散区增益会出现峰值,随后增益随Δk2和z/L的增加而逐渐减小。讨论了反斯托克斯波与斯托克斯波Eax/Esx的比值随失配系数Δk2的增加而快速衰减的变化特性。     

Molecular dynamics simulations of La2O3 thin films on SiO2

Classical molecular dynamics is used to investigate the equilibrium state of the surface region and interface of heteroepitaxial La2O3 thin films.Due to the lattice mismatch,heteroepitaxial thin films are subject to very large stress.For this reason the behavior of La2O3 thin films at SiO2interface becomes an important concern.Our result indicates that La2O3 can uniformly wet SiO2 surface.The properties of the simulated films are analyzed and the lack of any discernible crystalline phase in epitaxial La2O3 on SiO2 indicates that the lattice mismatch between SiO2 and La2O3 is sufficiently large to prevent the formation of even short-range orders in La2O3 film.     

失配因子σ2对掺杂锰基钙钛矿氧化物输运性质的影响

掺杂量、A位阳离子平均半径及失配因子是影响掺杂锰基钙钛矿氧化物从顺磁绝缘体到铁磁金属转变的主要因素，为了突出研究失配因子的影响，本文固定掺杂量和A位阳离子平均半径制备了一系列样品。0和5T磁场下电阻率与温度关系测量表明，随着失配因子的增加，绝缘体-金属转变温度向低温区移动且与σ^2岩保持线性关系；通过调节失配因子，样品La0.53Sm0.17Sr0.3MnO3的磁电阻在室温附近达到了极大值。结合样品的电输运行为，对实验结果进行了讨论。     

Cross-phase modulational instability in an elliptical birefringent fiber with higher order nonlinearity and dispersion

We obtain conditions for the occurrence of cross-phase modulational instability in the normal dispersion regime for the coupled higher order nonlinear Schrödinger equation with higher order dispersion and nonlinear terms.     

Multidimensional Polyhedral Gamut Representation of Reflective Objects and Calculation of Metamer Ensembles

The spectral reflectance of most reflective objects, such as natural objects and color hardcopy, is relatively smooth and can be approximated by several principal components with high accuracy. Although the subspace spanned by those principal components represents a space in which reflective objects exist, it does not provide the limit of the object distribution or the gamut. In this paper we propose to represent the gamut of reflective objects as a convex polyhedron in the subspace spanned by several principal components. The concept of the polyhedral gamut representation based on the spectral reflectance database and its application to the calculation of metamer ensembles are described. The color-mismatch volume caused by different illuminant and/or observer for a metamer ensemble is also calculated and compared with the theoretical ones.     

Study of synchronously mode-locked and internally frequency-doubledcw dye laser

The analysis of the characteristics of a synchronously mode-locked and internally frequency-doubled dye laser is presented. Dependence of dye laser pulse characteristics on the cavity length mismatch of the pump laser and dye laser is studied. Variation of the minimum pulsewidth with intracavity bandwidth and the harmonic conversion efficiency is presented in the form of graphs.     

Experimental research on measuring the fine structure of long pulse in time domain by synchronized ultrashort pulse

We propose a method of measuring the fine structure of a long pulse in time domain by a synchronized ultrashort pulse, in which the basic principle is the cross-correlation interaction between the long pulse and the ultrashort pulse in a nonlinear crystal. After a theoretical analysis on the principle and resolution, as an example, the fine structure of a picosecond Nd:YLF laser pulse is characterized by a synchronized femtosecond pulse experimentally. Further, the effect of group velocity mismatch on measurement results is discussed.