Polyoxometalate-cucurbituril molecular solid as photocatalyst for dye degradation under visible light

An organic-inorganic hybrid molecular solid based on Lindqvist-type polyoxometalate (POM) anions, {W₆O₁₉}^2 −, and decamethylcucurbit[5]uril (Me₁₀CB[5]) was synthesized under hydrothermal condition. In the structure of {[Na₂(W₆O₁₉)(Me₁₀CB[5])(H₂O)]·2H₂O}_n (complex 1), the sodium cations, {W₆O₁₉}^2 − anions, and Me₁₀CB[5] macrocycles formed a 1D chain subunit that assembled into a 3D supramolecular host-guest network through extensive supramolecular interactions. Furthermore, the complex displayed enhanced photocatalytic activity towards the degradation of rhodamine B (RhB) in water under visible light irradiation.     

A pillar-layer MOF used as a luminescent probe for detecting small molecules acetone

The reactions of 4,4-bipyridine and 5-Hydroxyisophthalic acid with Zn(NO₃)₂·3H₂O in N,N′-dimethylacetamide lead to the formation of [Zn(5-hip)(bpy)]·2DMA (1). Compound 1 possesses a non-interpenetrating pillar-layer framework with 1D rectangular-shape channels. The experimental results show that the luminescent intensity of 1 highly depends on small solvent molecules, particularly CH₃OH and acetone. Compound 1 can be used as a luminescent probe to detect small molecule acetone.     

Selected product ion monitoring for quantification of 5-hydroxymethylfurfural in food products by capillary zone electrophoresis-tandem ion trap mass spectrometry

5-hydroxymethylfurfural (HMF) is an important marker of food processing and storage widely recognized as an important parameter of food freshness and quality. Its amount depends on the composition of a food product and on the thermal treatments to which the food is subjected. The aim of this work was to propose for the first time the optimization and validation of an innovative CE-MS² method for the quantification of HMF in food products exploiting selected product ion monitoring as acquisition mode. The method was applied to the analysis of different kind of samples: cereal-based baby foods, coffee, soft beverages and vinegars. In order to show the reliability of the proposed method, results were compared with those obtained by RP-HPLC-UV, and a good accordance between the two sets of data was found.     

Modeling structure–activity relationships of prodiginines with antimalarial activity using GA/MLR and OPS/PLS

In the present study, we performed a multivariate quantitative structure-activity relationship (QSAR) analysis of 52 prodiginines with antimalarial activity. Variable selection was based on the genetic algorithm (GA) and ordered predictor selection (OPS) approaches, and the models were built using the multiple linear regression (MLR) and partial least squares (PLS) regression methods. The leave-N-out crossvalidation and y-randomization tests showed that the models were robust and free from chance correlation. The mechanistic interpretation of the results was supported by earlier findings. In addition, the comparison of our models with those previously described indicated that the OPS/PLS-based model had a higher quality of external prediction. Thus, this study provides a comprehensive approach to the evaluation of the antimalarial activity of prodiginines, which may be used as a support tool in designing new therapeutic agents for malaria.     

Additional doping of phosphorus into polypyrrole functionalized nitrogenous carbon nanotubes as novel metal-free oxygen reduction electrocatalyst in alkaline solution

Novel phosphorus-doped polypyrrole functionalized nitrogenous carbon nanotubes (P/NCNTs) was developed for the first time as metal-free electrocatalyst for enhancing the oxygen reduction reaction (ORR) activity in alkaline medium. The P/NCNTs was successfully synthesized by pyrolyzing PPy and triphenylphosphane (TPP) under N₂, using pyrrole as carbon and nitrogen precursors, TPP as phosphorus precursor. Various characterizations such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectra, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) reveal that the P/NCNTs material has covalently bound P atoms with carbon framework, which can introduce defect sites and can induce uneven charge distribution. Moreover, the content of pyridine N increased after P-doping, which is of great significance in improving the ORR activity. The electrochemical behavior of the resultant material shows that the P/NCNTs has much enhanced electroactivity and better stability for ORR. Additionally, a direct four-electron pathway occurred efficiently on P/NCNTs modified electrode. These enhanced performances indicate that P/NCNTs catalyst may be an excellent cathode catalyst for ORR.     

Multicolor electrochromic ultrathin films based on neutral red and polyoxometalate

Electrochromic ultrathin films composed of the polyoxometalate cluster K₁₀[P₂W₁₇O₆₁]·17H₂O (P₂W₁₇), polyallylamine hydrochloride (PAH) and Neutral Red (NR) were fabricated on quartz, silicon wafer and indium-tin oxide substrates by the layer-by-layer self-assembly method. The multilayer [P₂W₁₇/PAH/P₂W₁₇/NR]_n films were characterized by UV-vis spectroscopy, scanning electron microscopy, cyclic voltammetry and chronoamperometry and in-situ spectral electrochemical measurements, which exhibited suitable response time, high optical contrast and low operation potential. The monolacunary polyoxometalate-based electrochromic film displays adjustable colors and undergoes transitions from deep pink to light purple, then to dark purple-blue over the potential range from +0.2 V to − 1.0 V. Furthermore, two types of data storage using optical changes of the [P₂W₁₇/PAH/P₂W₁₇/NR]₃₅ film are proposed. The results provide valuable information for exploring applications in tunable-color electrochromic devices and data-storage devices.     

Spatial pattern of population mobility among cities in China: Case study of the National Day plus Mid-Autumn Festival based on Tencent migration data

Population migration, social check-in, vehicle navigation, and other spatial behavior big data have become vital carriers characterizing users' spatial behavior. “Tencent Migration” big data can real-timely, dynamically, completely and systematically record population flow routs using LBS device. Through gathering residents daily mobility among 299 cities in China during the period of “National Day–Mid-Autumn Festival” (NDMAF) vacation (from September 30 to October 8) in 2017 in “Tencent Migration” and defining three periods with “travel period, journey period, return period”, this paper is designed to analyze and explore the characteristics and spatial patterns of daily flow mobility cities from the perspective of population daily mobility distribution levels, flow distribution layers network aggregation, spatial patterns and characteristics of the complex structure of the flow network. Results show that “Tencent migration” big data clearly discovers the temporal-spatial pattern of population mobility in China during the period of NDMAF. The net inflow of population showed a diamond shaped with cross frame support in each period, the four nodes of the diamond contain Beijing, Shanghai, Guangzhou and Xi'an. Main mobility assembling centers are distributed in the urban agglomerations of Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta and Chengdu-Chongqing, and those centers have strong coherence with those urban hierarchies. Most cities are in a state of “relative equilibrium” in the population flow, and clear hierarchical structure and level distinction can be identified. Spatial patterns of population mobility present obvious core-periphery structures. The Dali-Hegang line exhibits a significant network of spatial differences in terms of boundary divisions. In this context, the spatial distribution of urban network could be summarized as “dense in the East and sparse in the West”, and the core linkages of urban network could be characterized as “parallel in the East and series in the West”. The whole network exhibits a typical “small world” network characteristic, which shows that China's urban population flow network has high connectivity and accessibility during the period of NDMAF. The network has a distinct “community” structure in the local area, including 2 national communities, 2 regional communities and 3 local-level communities.     

Defects characterization of Dy-doped BaTiO3 ceramics via electron paramagnetic resonance

The point defects and the structural and dielectric properties of Dy-doped BaTiO₃ ceramics prepared at 1400 °C were investigated. The solubility of Dy in the self-compensation mode was determined to be x = 0.07 for (Ba_1−xDy_x)(Ti_1−xDy_x)O₃, and no EPR signals associated with the Dy³⁺ Kramers ion or the Ba and Ti vacancies were detected using the electron paramagnetic resonance (EPR) technique. As x increases, the dielectric behavior changed from a first-order phase transition to a diffuse phase transition to a Y7R dielectric-temperature stability. A strong EPR signal at g = 1.974, which is rare among rare-earth-doped BaTiO₃ ceramics appeared unexpectedly in the single-phase (Ba_1−xDy_x)Ti_1−x/4O₃ ceramics with deliberately designed Ti vacancies. This signal was attributed to ionized Ba vacancy defects. A preference for the self-compensation mode of Dy³⁺ ions is responsible for the appearance of Ba vacancies. The real formula of the nominal (Ba_1−xDy_x)Ti_1−x/4O₃ is expressed as (Ba_1−xDy_3x/4)(Ti_1−x/4Dy_x/4)O₃. In addition, the defect chemistry is discussed.     

一种抗遮挡的运动目标跟踪算法

提出了一种基于彩色特征的抗遮挡目标跟踪算法。利用mean shift递推寻找当前帧目标的位置,并通过Kalman滤波估计目标状态。选用对目标部分遮挡具有鲁棒性的加权量化彩色直方图作为目标特征的概率分布,用Bhattacharyya系数作为特征相似性度量。提出一种目标遮挡因子,作为目标被遮挡程度的判断根据。当目标严重遮挡后,观测位置不再满足Kalman滤波的条件,采用目标状态量外推取代Kalman状态更新来预测目标当前的位置。实验结果表明,此方法对于部分遮挡以及全遮挡有较好的鲁棒性。