基于Ce4+/Ce3+转换的氧化还原荧光开关

通过简便的水热合成的方法,以稀土硝酸盐和三聚磷酸钠为原料,CePO4∶Tb3荧光纳米晶被成功制备.该纳米晶具有良好的稳定性和分散性.利用氧化还原反应诱导实现Ce4+/Ce3+之间的转换,能够有效地控制CePO4∶Tb3+荧光纳米晶的荧光“开”或“关”.在此文中,Fe3+作为氧化剂、抗坏血酸作为还原剂实现Ce4+/Ce3...     

Fluctuations of the total number of critical points of random spherical harmonics

We determine the asymptotic law for the fluctuations of the total number of critical points of random Gaussian spherical harmonics in the high degree limit. Our results have implications on the sophistication degree of an appropriate percolation process for modelling nodal domains of eigenfunctions on generic compact surfaces or billiards.     

Pharmacophore based 3D-QSAR modeling,virtual screening and docking for identification of potential inhibitors of β-secretase

The enzyme β-secretase-1 is responsible for the cleavage of the amyloid precursor protein, a vital step in the process of the formation of amyloid-β peptides which are known to lead to neurodegeneration causing Alzheimer’s disease. Challenges associated with toxicity and blood brain permeation inability of potential inhibitors, continue to evade a successful therapy, thus demanding the search and development of highly active and effective inhibitors. Towards these efforts, we used a ligand based pharmacophore model generation from a dataset of known inhibitors whose activities against β-secretase hovered in the nano molar range. The identified 5 feature pharmacophore model, AHHPR, was validated via three dimensional quantitative structure activity relationship as indicated by r², q² and Pearson R values of 0.9013, 0.7726 and 0.9041 respectively. For a dataset of compounds with nano molar activity, the important pharmacophore features present in the current model appear to be similar with those observed in the models resulting from much wider activity range of inhibitors. Virtual screening of the ChemBridge CNS-Set™, a database having compounds with a better suitability for central nervous system based disorders followed by docking and analysis of the ligand protein interactions resulted in the identification of eight prospective compounds with considerable diversity. The current pharmacophore model can thus be useful for the identification, design and development of potent β-secretase inhibitors which by optimization can be potential therapeutics for Alzheimer’s disease.     

Optimisation of laboratory arsenic analysis for groundwaters of West Bengal,India and possible water testing strategy

Regular monitoring of arsenic (As) in groundwater is crucial from public health perspectives as millions of people are suffering due to use of contaminated aquifer water for drinking purposes. The routine analyses, especially in developing nations, are mostly done in localised government/non-government laboratories with limited resources, having the target of analysing large number of samples in each run. Thus apart from analytical sensitivity, cost-effectiveness of the method and eco-friendliness of the experimental operation are key surreptitious factors. This demands optimisation of total As measurement methods and finding a method that gives ‘optimum benefit’ considering all these factors together. The present study therefore evaluates four common As (total) measurement methods [iodometric-colorimetric method, silver diethyl dithiocarbamate method, molybdenum blue method and hydride generation atomic absorption spectrophotometric (HG-AAS) method] practised in the Bengal Delta Plain, in view of their analytical sensitivity, related environmental hazard and experimental costs. It was found that the HG-AAS method is analytically more sensitive, whereas the iodometric-colorimetric method and the molybdenum blue method are better choices in terms of eco-friendliness and cost-effectiveness, respectively. However, when all three factors (analytical reliability, environmental hazard and cost) are considered simultaneously, the molybdenum blue method was found to be placed first in the ‘optimum performance rank’ list. It was also found that both environmental hazard and cost play a more crucial role than analytical reliability, although this is case specific and would differ from place to place around the globe. Finally based on the results, we have hypothesised a water testing strategy for developing countries such as India where the molybdenum blue method can be adapted as a screening method and later the HG-AAS method can be used to precisely identify the groundwater samples with As concentration below the WHO drinking water guideline value of 10 μg/L.     

研究激发态的多体格林函数理论

本文介绍的多体格林函数理论是一种建立在一套格林函数(包括单粒子格林函数和双粒子格林函数)方程基础上的,用以研究物质激发态性质的第一性原理方法。该理论包括计算准粒子性质的GW方法和描述电子-空穴对运动的Bethe-Salpeter方程。GW方法可以以很高的精度计算轨道能量、能带结构、准粒子寿命等物理量;Bethe-Salpeter方程则在研究激发能、光吸收谱、激发态动力学等光学性质上有广泛的应用前景。多体格林函数理论通过自能算符描述电子之间以及电子与空穴之间的交换关联作用。本文将详细阐述该理论的基本概念和原理,并对其在各种材料中的应用做简要介绍。     

一个含零齐次核的Hilbert型积分不等式

引进一个零齐次混合核,利用分析的方法和不等式理论,建立了一个舍参量且具有最佳常数因子的Hilbert型积分不等式及其等价形式．     

Structure dependent elastic properties of supergraphene

Complete replacement of aromatic carbon bonds in graphene by carbyne chains gives rise to supergraphene whose mechanical properties are expected to depend on its structure. However, this dependence is to date unclear. In this paper, explicit expressions for the in-plane stiffness and Poisson’s ratio of supergraphene are obtained using a mole-cular mechanics model. The theoretical results show that the in-plane stiffness of supergraphene is drastically (at least one order) smaller than that of graphene, whereas its Pois-son’s ratio is higher than 0.5. As the index number increases (i.e., the length of carbyne chains increases and the bond density decreases), the in-plane stiffness of supergraphene decreases while the Poisson’s ratio increases. By analyzing the relation among the layer modulus, in-plane stiffness and Poisson’s ratio, it is revealed that the mechanism of the faster decrease in the in-plane stiffness than the bond density is due to the increase of Poisson’s ratio. These findings are useful for future applications of supergraphene in nanomechanical systems.     

A direct probabilistic approach to solve state equations for nonlinear systems under random excitation

In this paper, a direct probabilistic approach (DPA) is presented to formulate and solve moment equations for nonlinear systems excited by environmental loads that can be either a stationary or nonstationary random process. The proposed method has the advantage of obtaining the response’s moments directly from the initial conditions and statistical characteristics of the corresponding external exci-tations. First, the response’s moment equations are directly derived based on a DPA, which is completely independent of the It?/filtering approach since no specific assumptions regarding the correlation structure of excitation are made. By solving them under Gaussian closure, the response’s moments can be obtained. Subsequently, a multiscale algo-rithm for the numerical solution of moment equations is exploited to improve computational efficiency and avoid much wall-clock time. Finally, a comparison of the results with Monte Carlo (MC) simulation gives good agreement. Furthermore, the advantage of the multiscale algorithm in terms of efficiency is also demonstrated by an engineering example.     

O,O-二丁基二硫代磷酸锌制备及光谱分析

采用二步法合成出O,O-二丁基二硫代磷酸锌(ZBPD),通过UV-Vis,FTIR,TG-DSC对其进行检测和表征,揭示出ZBPD的微观结构和内在规律性。UV-Vis检测出了ZBPD在212.0和227.0 nm有二个吸收峰,分别是n→σ*和π→π*电子跃迁产生的,吸收峰强度随ZBPD浓度呈规律性变化,为企业ZBPD产品质量检测,提供了基础数据。FTIR揭示了ZBPD分子内部的各元素之间的化学键键型。TG-DSC检测出ZBPD的质量变化与热效应两种信息,ZBPD的DSC曲线很复杂,84.3 ℃存在一个很宽的吸收峰,245.0,344.3,476.1,518.7 ℃存在四个放热峰,和ZBPD分子结构和少量杂质有关,ZBPD分解温度偏高,为采用硫化仪研究ZBPD的橡胶硫化性能提供参考。本研究为企业选定工作标准品,对ZBPD工业化生产进行跟踪检测,评判ZBPD的产品性能指标,填报立项ZBPD化工行业标准的申报,撰写标准草案提供基础实验数据。