立体角在结构化学中的应用

The concept of solid angle is used to explain the necessary and sufficient conditions for a three-dimensional gapless structure to be achieved by combining one or several polyhedrons. In this paper, the solid angle and dihedral angle of the common regular polyhedron and the common Archimedean semi regular polyhedron are presented, and the examples of structural chemistry are analyzed. In space, the sum of solid angles must be equal to 4π(sr), so by simply adding, we can judge the possibility of gapless accumulation, know the common situation of each point, and then deduce the space structure. By using this method, we can predict some structures that do not exist yet.     

基于“1+2”模式的结构化学课程在线教学实践

Since the outbreak of novel coronavirus pneumonia (NCP) at the beginning of this year, Chinese government acted immediately and made some regulations to control the epidemic NCP and promote the recovery of society and industry including education. Chinese universities stayed on the online courses without suspension on teaching and learning. Herein, we report online teaching of structural chemistry course based on the teaching mode of online live broadcast platform, online course resources and management platforms ("1 + 2" mode). This may promote online teaching, and take advantage of online live broadcast and massive open online courses, which achieves good teaching and learning experiences on structural chemistry course.     

Strong and Superhydrophobic Wood with Aligned Cellulose Nanofibers as a Waterproof Structural Material†

Lightweight structural materials are important for the energy efficiency of applications, particularly those in the building sector. Here, inspired by nature, we developed a strong, superhydrophobic, yet lightweight material by simple in situ growth of nano‐SiO₂ and subsequent densification of the wood substrate. In situ generation of SiO₂ nanoparticles both inside the wood channels and on the wood surfaces gives the material superhydrophobicity, with static and dynamic contact angles of 159.4^o and 3^o, respectively. Densification of the wood to remove most of the spaces among the lumen and cell walls results in a laminated, dense structure, with aligned cellulose nanofibers, which in turn contributes to a high mechanical strength up to 384.2 MPa (7‐times higher than natural wood). Such treatment enables the strong and superhydrophobic wood (SH‐Wood) to be stable and have excellent water, acid, and alkaline resistance. The high mechanical strength of SH‐Wood combined with its excellent structural stability in harsh environments, as well its low density, positions the strong and superhydrophobic wood as a promising candidate for strong, lightweight, and durable structural materials that could potentially replace steel.     

An overview of emerging pollutants in air: Method of analysis and potential public health concern from human environmental exposure

Air pollutants are perhaps the largest cause of diseases and death in the world today. Increasing urbanization and industrialization have caused an increase in number of diverse forms and types of new pollutants, which are difficult to detect and characterize due to their stench behaviour and complex sources of production. Such pollutants have been called emerging pollutants (EPs) and their list is ever increasing. Therefore, the understanding of the method of analysis and health implication of (EPs) in air is critical to providing a more robust understanding of exposure routes, regulations and mitigation. EPs in air discussed in this study are not in any way exhaustive but limited to emerging VOCs (including acrylonitrile, 1−3-butadiene, chloroform, dichloromethane, ethylene oxides, formaldehyde, toluene, trichloroethylene, 1,4-Dioxane) and metals (arsenic, manganese, and vanadium), ultrafine particles, micro- and nano- plastics, engineered nanoparticles, diesel/black carbon and bioaerosols. Occurrence, detection and health implications of these EPs in air are still unfolding due to limited monitoring studies, lack of standard methodology and regulations. To address this knowledge gap, authors conducted an in-depth review of available information. Their spatial distribution, analytical methods and health implications are discussed including the novel coronavirus (COVID-19) as a potential EP in air. The study concluded with highlights of gaps in knowledge and suggestions to key areas for future research. This information is of general interest to environmental scientists and of specific interest to both health and sanitation workers and policymakers at private, government and international organizations.     

Cheminformatics in MS-based environmental exposomics: Current achievements and future directions

Compound annotation using MS/MS data is the major bottleneck in interpretation of mass spectrometry data during non-targeted screening and suspect screening exposomics studies. Apart from compound identification using available databases or mass spectral libraries, the true challenge comes when completely new compounds have to be identified. Along with recent advances in MS instrumentation that set grounds to a new revolutionary age in environmental exposomics, a multitude of cheminformatics annotation approaches has been developed. Herein, we review the basic principles of the cutting-edge cheminformatics MS-based approaches employed in eco-exposome annotation.We give a solid background discussing the eco-exposome concept in relation to the advances in MS instrumentation, and define the three crucial cheminformatics tasks used in the eco-exposome annotation: molecular formula assignment, compound prioritization and compound annotation. The basic principles of compound annotation are discussed, which are based on three approaches of utilizing structural information inherent to MS data. These involve direct, indirect and joint annotation approaches. We assess their performance through the ability to annotate eco-exposome constituents. We discuss future perspectives and give directions to new annotation strategies and performance evaluation protocols aiming to solve current issues hampering the incorporation of cheminformatics annotation approaches in regular eco-exposome annotation workflows.     

Recent progress in measurements of oscillatory forces and liquid properties under confinement

The present review paper focuses on direct measurements of oscillatory forces. Beside the surface forces apparatus (SFA), atomic force microscopy (AFM) has emerged as the most commonly used technique to measure surface forces. Recent instrumental advances of both methods are highlighted in the review. Different systems, showing oscillatory forces are classified. Principle distinction is made between 1-component liquids (water, organic liquids and liquid crystals), pseudo 1-component liquids (ionic liquids and microemulsions) and 2-component liquids (dispersions containing polyelectrolytes, micelles or nanoparticles). In the last few years, the oscillatory force studies address particle characterisation, synergistic effects in multicomponent systems, the introduction of ‘switchable’ forces, and resolving liquid properties under confinement. Last but not least, the ability of AFM and SFA to measure oscillatory forces is discussed.     

Accumulation of selected metals in the fruits of medicinal plants grown in urban environment of Islamabad,Pakistan

The present study is based on the measurement of selected metals (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Pb, Sr and Zn) in the fruits of eight medicinal plants (Carrisa opeca, Phyllanthus emblica, Solanum nigrum, Zizyphus nummularia, Zizyphus mauritiana, Physalis minima, Opuntia dillenii and Phoenix dactylifera) and relevant soil samples by atomic absorption spectrometry. Highest average concentrations of Cu (14.4 mg/kg), Cr (19.0 mg/kg), and Zn (125 mg/kg) were found in the fruits of P. minima, C. opeca and Z. nummularia, respectively, while O. dillenii showed the elevated mean levels of Cd (3.49 mg/kg), Sr (61.4 mg/kg), Mg (0.21%), Ca (6.62%) and Mn (44.6 mg/kg). However, highest average levels of Pb (41.7 mg/kg) and Co (38.4 mg/kg) were found in Z. mauritiana. Overall, most of the fruit samples showed higher contributions of Ca and Mg, followed by Fe, Zn, Co and Pb. In the case of soil samples, highest concentration was observed for Ca, followed by Fe, Mg, Mn and Sr, while lowest concentration was shown by Cd. Bioaccumulation factors exhibited significantly higher accumulation of Co (0.813–1.829) and Pb (0.060–2.350) from the soil to the fruits. Principal component analysis revealed significant anthropogenic contributions of Pb, Fe and Co in the fruit samples. Contamination factors and enrichment factors of Cd and Pb in the soil indicated very high contamination and extreme enrichment of these metals.     

无机二元氢化物酸性的径向基函数神经网络研究

用径向基函数神经网络(RBF-Network)构建了一个无机二元氢化物酸性强度pKa与结构参数的非线性关联模型。13个样本的pKa计算值与实验值相关系数R达到0·9998,平均偏差0·315,显著优于文献报道的结果。交互预测的结果也非常理想,Rcv达到0·9984。参数试验的结果显示,以键合氢原子数m表征的构型因素和以键长rA—H等表征的分子大小因素是影响无机二元氢化物酸性强弱的主要影响因素。     

Phase stability and temperature effect in ScX (X=S,Se and Te) compounds

Based on first-principles calculations, the structural stability and temperature effect in ScX (X=S, Se and Te) compounds are studied with three typical structures of B1 (NaCl-type), hcp (NiAs-type) and β-hcp (inverse Li₂O₂-type). Their dynamic stability has been verified using phonon mode analysis and molecular dynamics simulations. From the total energy calculations, we find that the most stable ground state structures are B1 for ScS, and hcp for ScSe and ScTe, respectively. Moreover, structural stabilities at finite temperature are studied with the combination of phonon dependent dynamics analysis and first-principles calculations, which reveals a phase transition from hcp to B1 in ScSe around 230 K and a phase transition from hcp to β-hcp in ScTe around 460 K, in accordance with experimental findings. The energy barrier and pathway along the phase transformation from hcp to β-hcp ScTe are also calculated and analyzed by the solid-state nudged elastic band method.     

Analysis in protein profile,antioxidant activity and structure-activity relationship based on ultrasound-assisted liquid-state fermentation of soybean meal with Bacillus subtilis

This study investigated effects of ultrasound on the contents of peptide and soluble protein, antioxidant activity, functionalities and structural characteristics of fermented soybean meal (FSBM) with Bacillus subtilis systematically. The results showed that there were significant effects of ultrasound treatments (frequency, treatment time and power density) on the contents of peptide and soluble protein (p < 0.05). Under the optimum ultrasound conditions (power density of 0.08 W/mL, frequency of 33 kHz and treatment time of 1 h) by single factor experiment, the contents of peptide and soluble protein increased by 31.27% and 18.79% compared to those of the control, respectively. Additionally, the in vitro antioxidant activity (•OH scavenging rate, Fe²⁺ chelating capacity and DPPH radical scavenging rate) and functional properties (emulsifying activity and emulsifying stability) of FSBM were found to be noticeably improved by ultrasound (p < 0.05). The fourier transform infrared (FTIR) spectroscopy revealed that ultrasound caused protein molecules to unfold with a decrease content of α-helix and β-turn and an increase in the proportion of β-sheet and random coil. Besides, atomic force microscope (AFM) results indicated that ultrasonication generally increased the surface roughness of protein and the protein sonicated with higher frequency (≥33 kHz) exhibited a greater height compared to lower frequency ultrasonication. Structure-activity relationship analysis illustrated that there was a good linear relationship between •OH scavenging rate and β-sheet/β-turn with Pearson’s correlation coefficient r of −0.86/0.90. Collectively, the selection of ultrasonic parameters is essential for the preparation of functional protein and bioactive peptide by enhancing fermentation of agroindustrial by-products.