Assembling SnO2 nanocubes to nanospheres for high-sensitivity sensors

SnO₂ nanospheres with a diameter of about 150 nm were synthesized by a hydrothermal method. They were assembled by numerous tetragonal nanocubes with an average size of 8 nm. Since the morphology of nanospheres agglomerated by nanocubes, the modulations of quantum confinement and large contact area were realized; this would serve as the basis for high sensitivity. The sensors based on the as-synthesized nanospheres showed good selectivity among different gases and superior sensitivity to ethanol compare with previous reports. The sensitivity could reach 53 to 50 ppm ethanol at a relatively low working temperature of 275 °C. A possible mechanism was proposed, which could be primarily related to the large surface-to-volume ratio and the small size effect of nanocubes.     

Design of rapidly synergistic cloud point extraction of ultra-trace lead combined with flame atomic absorption spectrometry determination

In this work, traditional cloud point extraction (CPE) pattern was changed and improved by the proposed rapidly synergistic CPE. Using octanol as cloud point revulsant and synergic reagent, non-ionic surfactant Triton X-114 (TX-114) accomplished room temperature extraction rapidly without heating in water bath. The improved extraction was named as rapidly synergistic cloud point extraction (RS-CPE). Compared with traditional CPE, RS-CPE was accomplished in 1 min with considerably high extraction efficiency. The improved CPE pattern was coupled with flame atomic absorption spectrometry (FAAS) for the extraction and detection of trace lead in real and certified water samples with satisfactory analytical results. The proposed method greatly improved the sensitivity of FAAS for the determination of lead. Under the optimal conditions, the limit of detection (LOD) for lead was 4.3 μg/L, with enhancement factor (EF) of 39. Factors influencing RS-CPE efficiency, such as concentrations of surfactant TX-114 and octanol, concentration of chelating agent, pH, conditions of phase separation, environmental temperature, salt effect and instrumental conditions, were studied systematically.     

Robust synchronization and anti-synchronization of identical Φ6 oscillators via adaptive sliding mode control

The main goal of this paper is to propose the single input robust adaptive sliding mode controllers to accomplish synchronization and anti-synchronization between two identical Φ⁶ Duffing or Van der Pol oscillators with unmodel dynamics and external disturbances. Unlike directly eliminating the nonlinear dynamics by active control and sliding mode control in the literature, the proposed sliding mode controllers include the equivalent control part, which is only proportional to the synchronized error states, and the switching control part, where the discontinuous control functions have adaptive feedback gains. Sufficient conditions are provided based on the Lyapunov stability theorem and numerical simulations are performed to verify the effectiveness of presented schemes.     

Transition kinetics of impurity doped quantum dots driven by sinusoidal field: Role of Gaussian white noise

Present study delves into understanding the role of Gaussian white noise on time-average excitation rate (TAER)of impurity doped quantum dot (QD). The TAER profiles have been meticulously scrutinized as a number of physical quantities vary over a range with and without noise. Application of noise to the system has been carried out in two different pathways known as ’additive’ and ’multiplicative’. The excitation of ground state electronic population to the higher states is driven by an external sinusoidal field. On most occasions the TAER profiles exhibit lots of undulations. In addition to this, the said profiles also comprise of features like maximization, minimization and saturation. However, the very nature of the features of a particular profile depends on presence/absence of noise, the noise mode and the identity of the physical quantity undergoing change. Introduction of multiplicative noise of some typical strength emerges to be facilitative for production of high TAER.     

POSITIVE SOLUTIONS FOR SINGULAR BOUNDARY VALUE PROBLEM OF SECOND ORDER

Some results of existence of positive solutions for singular boundary value problems{-u"(t)=p(t)f(u(t)), t∈(0,1), u(0)=u(1)=0are given, where the function p(t) may be singular at t = 0, 1.     

λ-超凸空间中的一个选择定理及其应用

本文研究度量空间中取非空λ外超凸值的集值映象的选择问题.利用Zorn引理,得到了一个选择定理.作为应用,得到了一个不动点定理,并且证明了有界λ超凸空间中1λLipschitzian集值映象的不动点集为λ超凸集.     

A New Taxoid from Leaves and Branches of Taxus chinensis

A new taxoid, 2-deacetyl-2α, 14β-dihydroxybaccatin Ⅳ (1), was isolated from the leaves and branches of Taxus chinensis together with the known compound baccatin Ⅳ (2). The structure of the new compound was elucidated by spectroscopic techniques. The detailed ^13C NMR assignments of baccatin Ⅳ are reported for the first time.     

Investigation of chemical changes in Polygonatum kingianum after traditional processing by multiple fingerprint profiles in combination with multivariate methods

Polygonati Rhizoma (Huangjing) is traditional medicine in China, which can only be used as medicine after being processed. However, there is a limited theoretical basis for analyzing the changes in chemical components after traditional processing. In this study, analytical techniques including Fourier transform infrared spectroscopy, high-performance gel permeation chromatography–evaporative light scattering detection, and HPLC–diode array detection were proposed to perform multiple fingerprint analyses of the changes in the processed materials; the total sugar was also determined. Moreover, the chemometric studies, including hierarchical cluster analysis and principal component analysis, were used to visualize the discrimination of raw and processed materials. The results revealed that the chemical constituents had been profoundly changed following sample processing. In conclusion, these methods could be successfully used to compare raw and processed materials of Polygonatum kingianum, which could be used to elaborate the rationality of processing from the perspective of chemical composition.     

激光诱导击穿光谱和人工神经网络的青白色软玉产地溯源

建立基于激光诱导击穿光谱仪技术获取的半定量青白色软玉的微量元素含量的人工神经网络模型,以促进人工神经网络技术在宝石产地溯源方面的应用。以我国新疆、广西、江苏、青海,以及韩国和俄罗斯六个产地的青白色软玉为样品,利用激光诱导击穿光谱仪在颜色均匀干净的部分获取元素含量数据。使用数据筛选原则对数据进行了筛选和Al的归一化处理之后,以因子分析和线性回归分析讨论了数据间的共线性,在数据间不存在明显多重共线性的情况下建立了三层人工神经网络的判别模型。结果表明,所选取的每个变量的VIF值小于5,数据间不存在明显的多重共线性,因子分析的KMO值小于0.6,表明变量间无明显关系。同时利用软玉t-SNE图对数据进行降维和可视化处理,t-SNE图显示大部分数据点都重叠在一起,表明对此数据进行简单聚类和相关分析是无法区分产地的,因此选择人工神经网络的方法对六个产地的数据进行产地判别分析。经人工神经网络模型迭代判别之后,模型对我国新疆、广西、江苏、青海,以及韩国和俄罗斯六个产地的青白色软玉判别的精度达到0.933,其中韩国软玉的数据判别结果精度最高,达到0.995,误差为0.028,青海软玉的数据判别结果最低为0...