光谱法鉴定手性化合物的绝对构型——从仪器表征到理论计算

手性化合物的结构确定,尤其是新型手性化合物的绝对构型测定一直是不对称研究的重要工作.除单晶测试外,光谱学方法近年来被广泛应用于手性分子结构鉴定,主要包括电子和振动圆二色谱、旋光光谱、旋光拉曼谱等.本文对上述测试方法的原理、应用范围和相关理论计算方法做了介绍.把谱学测试与理论计算相结合,将成为手性分子结构鉴定的重要发展方向.     

Increasing the Chemical‐Shift Dispersion of Unstructured Proteins with a Covalent Lanthanide Shift Reagent

The study of intrinsically disordered proteins (IDPs) by NMR often suffers from highly overlapped resonances that prevent unambiguous chemical‐shift assignments, and data analysis that relies on well‐separated resonances. We present a covalent paramagnetic lanthanide‐binding tag (LBT) for increasing the chemical‐shift dispersion and facilitating the chemical‐shift assignment of challenging, repeat‐containing IDPs. Linkage of the DOTA‐based LBT to a cysteine residue induces pseudo‐contact shifts (PCS) for resonances more than 20 residues from the spin‐labeling site. This leads to increased chemical‐shift dispersion and decreased signal overlap, thereby greatly facilitating chemical‐shift assignment. This approach is applicable to IDPs of varying sizes and complexity, and is particularly helpful for repeat‐containing IDPs and low‐complexity regions. This results in improved efficiency for IDP analysis and binding studies.     

New (3+1)‐dimensional nonlinear equations with KdV equation constituting its main part: multiple soliton solutions

In thiswork,we present two new(3+1)‐dimensional nonlinear equationswith Korteweg‐de Vries equation constituting its main part. We show that the dispersive relation is distinct for each model, whereas the phase shift remains the same. We determine multiple solitons solutions, with distinct physical structures, for each established equation. The architectures of the simplified Hirota's method is implemented in this paper. The constraint conditions that fall out which must remain valid in order for themultiple solitons to exist are derived.Copyright © 2015 John Wiley & Sons, Ltd.     

中红外色散平坦渐减光纤设计

设计了一种以As2S3玻璃为纤芯、碲酸盐玻璃为微结构包层的锥形光子晶体光纤.该结构光纤兼具阶跃折射率光纤和光子晶体光纤双重特性,具有色散调制灵活性高且限制损耗低等优点.模拟结果表明:优化该光纤结构包层空气孔径、孔间距、纤芯直径等特征参量,使参量之间及参量与椎区长度之间满足特定线性关系时,该光纤在2~4.5μm中红外波段呈现色散平坦渐减特性;对该光纤微包层进行折射率~1.6的液体油填充处理,色散曲线对称性及平坦性得到进一步优化.该光纤在超短脉冲压缩与展宽、色散波、光孤子及中红外平坦超连续谱产生等领域应用潜力巨大.     

光伏阵列伏安特性测试系统设计

基于对光伏电站控制和设计水平的要求,本文提出一种基于电容充放电的特性的光伏阵列伏安特性测试系统。本文阐述了测试系统的工作原理和系统关键的部分。当光伏阵列给电容充电时,得到当时环境中光伏阵列的电压、电流以及相应的功率特性曲线。同时对M*N的光伏组件进行建模,得出组件的相应的电性能参数,并对最大功率点进行分析。最后进行实验验证。本测试系统具有测量精度高、系统稳定性高、成本低廉,并且能更直观的测得光伏阵列的特性。     

光纤中单光子传输方程的求解及分析

量子信息在光纤中传输时,会受到光纤损耗、色散、非线性效应等多因素的影响,将产生传输态的演化与能量转移.本文以单模光纤传输方程以及电磁场量子化理论为基础,对单模光纤中基模模场进行量子化处理,推导并建立了考虑损耗、色散、非线性效应后的单光子传输方程.基于微扰法对单光子非线性传输方程进行了求解,给出了稳定解存在的必要条件及其所满足的色散方程.深入讨论了广域光功率随微扰频率的变化关系,并且分析了光纤色散、非线性效应对解的影响.为量子光纤传输系统性能的深入研究奠定了理论基础.     

基于光纤振动安全预警系统的振源识别算法研究

光纤振动预警系统可自动采集周边振动信号,面对大量复杂的振动信号,如何准确识别目标振源是系统研究的难点。针对光纤振动安全预警系统采集到的振动信号进行属性特征分析,建立相应的特征模型,并建立振源属性特征模型,包括识别下雨振源的能量信息熵模型,以及区分机械施工和车辆经过振源的基频稳定性模型等。通过振源识别算法,提高了振源类型识别的准确性。测试结果表明,特征模型的设计和选择合理,识别准确率高。     

Effect of low frequency ultrasound on the surface properties of natural aluminosilicates

Structural and surface properties of different natural aluminosilicates (layered, chain and framework structural types) exposed of 20 kHz ultrasound irradiation (0–120 min) in aqueous and 35 wt%. aqueous H₂O₂ dispersions were studied by X-ray diffraction (XRD), dynamic light scattering (DLS), nitrogen adsorption–desorption, thermal analysis, and Fourier transform infrared spectroscopy (FTIR) techniques. It was confirmed that sonication caused slight changes in the structure of investigated minerals whereas their textural properties were significantly affected. The aqueous dispersions of montmorillonite (Mt), clinoptilolite (Zlt), glauconite (Glt) and palygorskite (Pal) were represented by several particles size fractions according to DLS-study. Ultrasound irradiation produced a decrease of the average particle diameter by 4–6 times in water and by 1.3–5 times in H₂O₂ dispersions except for Pal, which underwent strong agglomeration. A significant increase of total pore volume and pore diameter was observed for Glt sonicated in H₂O₂ dispersions whereas for Pal mainly micropore volume sharply increased in both aqueous and H₂O₂ dispersions.     

Optimisation of a matrix solid-phase dispersion method for the determination of organophosphate compounds in dust samples

A fast and inexpensive sample preparation procedure based on the matrix solid-phase dispersion (MSPD) technique is proposed for the isolation of several organophosphate esters (mainly employed as flame retardants and plasticizers) from indoor dust samples. Extraction and clean-up were carried out in a single step and target compounds were determined by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). The main parameters affecting extraction yield and selectivity, such as type and amount of dispersant material, clean-up co-sorbent and extraction solvent, were evaluated and optimised. Under final conditions, 0.5 g of dust were dispersed with equal amounts of anhydrous sodium sulphate and Florisil, and loaded on the top of a polypropylene cartridge containing 0.5 g of alumina. The dispersed sample was washed with 2 mL of n-hexane to remove the least polar interferences and analytes were eluted with 3 mL of acetone. Recoveries of the proposed method for spiked samples ranged from 80 to 116%, and the day-to-day variability remained between 5 and 10%. Data on levels of organophosphate species in dust from private houses and vehicle cabins are provided. In both cases, the lowest concentrations corresponded to the short chain, non-chlorinated, alkyl organophosphates, whereas mean values above 1 μg g⁻¹ were measured for the rest of analytes.