氧化镍纳米晶体的制备及其过程分析

为了开发一种新型纳米氧化镍催化剂,能有效地应用于生物质气化过程中去除焦油,本文采用均匀沉淀法成功地制备了纳米氧化镍晶体,并利用TGA、FTIR、XRD、BET、YEM等分析手段对前驱体和产品的性能进行了表征.同时,对前驱体的分解过程进行了全面的分析.分析结果表明前驱体是水合碱式碳酸镍,其分子式为NiCO3·Ni(OH)2·nH2O,它能在360℃下完全分解转化为纳米NiO,同时煅烧条件对合成纳米NiO的晶体粒径影响很大.实验证实所得纳米NiO颗粒呈球形,分散性好,纯度较高,属立方晶系结构,平均粒径约为7.5nm,其BET表面积为187.98m2/g,这显示纳米NiO晶体具有作为高效催化材料的应用可行性.     

An unexpected all-metal aromatic tetranuclear silver cluster in human copper chaperone Atox1

Metal clusters, such as iron–sulfur clusters, play key roles in sustaining life and are intimately involved in the functions of metalloproteins. Herein we report the formation and crystal structure of a planar square tetranuclear silver cluster when silver ions were mixed with human copper chaperone Atox1. Quantum chemical studies reveal that two Ag 5s¹ electrons in the tetranuclear silver cluster fully occupy the one bonding molecular orbital, with the assumption that this Ag₄ cluster is Ag₄²⁺, leading to extensive electron delocalization over the planar square and significant stabilization. This bonding pattern of the tetranuclear silver cluster represents an aromatic all-metal structure that follows a 4n + 2 electron counting rule (n = 0). This is the first time an all-metal aromatic silver cluster was observed in a protein.

Metal clusters, such as iron–sulfur clusters, play key roles in sustaining life and are intimately involved in the functions of metalloproteins.     

EGFAFS: A Novel Feature Selection Algorithm Based on Explosion Gravitation Field Algorithm

Feature selection (FS) is a vital step in data mining and machine learning, especially for analyzing the data in high-dimensional feature space. Gene expression data usually consist of a few samples characterized by high-dimensional feature space. As a result, they are not suitable to be processed by simple methods, such as the filter-based method. In this study, we propose a novel feature selection algorithm based on the Explosion Gravitation Field Algorithm, called EGFAFS. To reduce the dimensions of the feature space to acceptable dimensions, we constructed a recommended feature pool by a series of Random Forests based on the Gini index. Furthermore, by paying more attention to the features in the recommended feature pool, we can find the best subset more efficiently. To verify the performance of EGFAFS for FS, we tested EGFAFS on eight gene expression datasets compared with four heuristic-based FS methods (GA, PSO, SA, and DE) and four other FS methods (Boruta, HSICLasso, DNN-FS, and EGSG). The results show that EGFAFS has better performance for FS on gene expression data in terms of evaluation metrics, having more than the other eight FS algorithms. The genes selected by EGFAGS play an essential role in the differential co-expression network and some biological functions further demonstrate the success of EGFAFS for solving FS problems on gene expression data.     

Effect of Different Processing Methods on the Chemical Constituents of Scrophulariae Radix as Revealed by 2D NMR-Based Metabolomics

Scrophulariae Radix (SR) is one of the oldest and most frequently used Chinese herbs for oriental medicine in China. Before clinical use, the SR should be processed using different methods after harvest, such as steaming, “sweating”, and traditional fire-drying. In order to investigate the difference in chemical constituents using different processing methods, the two-dimensional (2D) ¹H-¹³C heteronuclear single quantum correlation (¹H-¹³C HSQC)-based metabolomics approach was applied to extensively characterize the difference in the chemical components in the extracts of SR processed using different processing methods. In total, 20 compounds were identified as potential chemical markers that changed significantly with different steaming durations. Seven compounds can be used as potential chemical markers to differentiate processing by sweating, hot-air drying, and steaming for 4 h. These findings could elucidate the change of chemical constituents of the processed SR and provide a guide for the processing. In addition, our protocol may represent a general approach to characterizing chemical compounds of traditional Chinese medicine (TCM) and therefore might be considered as a promising approach to exploring the scientific basis of traditional processing of TCM.     

HIGH-FREQUENCY VIBRATIONS OF CORRUGATED CYLINDRICAL PIEZOELECTRIC SHELLS

Coupled extensional and flexural cylindrical vibrations of a corrugated cylindrical piezoelectric shell consisting of multiple pieces of circular cylindrical surfaces smoothly connected along their generatrix are studied. To validate the results for the case of relatively thick shells or equivalently high-frequency modes with short wavelengths, existing analysis is extended by considering shear deformation and rotatory inertia. An analytical solution is obtained. Based on the solution, resonant frequencies and mode shapes are calculated.     

有雨概率与分维数关系的初步研究

对武汉地区１９８２～１９９４年有雨分维数与有雨概率之间的关系进行了初步的分析和研究，并给出了研究结果．为今后修改降雨衰减预报模型作准备．     

HSH-carbon: A novel sp2−sp3 carbon allotrope with an ultrawide energy gap

An sp²-sp³ hybrid carbon allotrope named HSH-carbon is proposed by the first-principles calculations. The structure of HSH-carbon can be regarded as a template polymerization of [1.1.1]propellane molecules in a hexagonal lattice, as well as, an AA stacking of recently reported HSH-C₁₀ consisting of carbon trigonal bipyramids. Based on calculations, the stability of this structure is demonstrated in terms of the cohesive energy, phonon dispersion, Born−Huang stability criteria, and ab initio molecular dynamics. HSH-carbon is predicted to be a semiconductor with an indirect energy gap of 3.56 eV at the PBE level or 4.80 eV at the HSE06 level. It is larger than the gap of Si and close to the gap of c-diamond, which indicates HSH-carbon is potentially an ultrawide bandgap semiconductor. The effective masses of carriers in the VB and CB edge are comparable with wide bandgap semiconductors such as GaN and ZnO. The elastic behavior of HSH-carbon such as bulk modulus, Young’s modulus and shear modulus is comparable with that of T-carbon and much smaller than that of c-diamond, which suggests that HSH-carbon would be much easier to be processed than c-diamond in practice.     

Effect of biaxial strain and hydrostatic pressure on the magnetic properties of bilayer CrI3

Two-dimensional van der Waals magnetic materials are intriguing for applications in the future spintronics devices, so it is crucial to explore strategy to control the magnetic properties. Here, we carried out first-principles calculations and Monte Carlo simulations to investigate the effect of biaxial strain and hydrostatic pressure on the magnetic properties of the bilayer CrI₃. We found that the magnetic anisotropy, intralayer and interlayer exchange interactions, and Curie temperature can be tuned by biaxial strain and hydrostatic pressure. Large compressive biaxial strain may induce a ferromagneticto-antiferromagnetic transition of both CrI₃ layers. The hydrostatic pressure could enhance the intralayer exchange interaction significantly and hence largely boost the Curie temperature. The effect of the biaxial strain and hydrostatic pressure revealed in the bilayer CrI₃ may be generalized to other two-dimensional magnetic materials.     

Optical properties of two-dimensional perovskites

The optical properties of two-dimensional (2D) perovskites recently receive numerous research focus thanks to the strong quantum and dielectric confinement effects. In addition to the strong excitonic effect at room temperature, 2D perovskites also have appealing features that their optical properties can be flexibly tuned by alternating organic or inorganic layers. Particularly, 2D chiral perovskites and 2D perovskites based heterostructures are emerging as new platforms to extend their functionalities. To optimize performance of 2D perovskites-based optoelectronic devices, it is critical to understand the fundamentals and explore the strategies to engineer their optical properties. This review begins with an introduction to the excitons and self-trapped excitons of 2D perovskites. Subsequently, inorganic/organic layer effects on optical properties and 2D perovskites based heterostructures are discussed. We also discussed the nonlinear optical properties of 2D perovskite. We are looking forward to that this review can stimulate more efforts to understand and optimize the optical properties of 2D perovskites.     

Proton Transfer of Phenanthridone in the Lowest Excited Singlet State in Moderately Concentrated Mineral Acid Solutions

A modified form of the steady state treatment for the determination of excited state proton transfer rate constants was successfully applied to a variety of oxygen and nitrogen center aromatic excited acids. These compounds shared the characteristic of being more acidic in the lowest excited singlet state (S₁) than in the ground electronic state (S₀) and of requiring a concentrated mineral acid medium for protonation. This treatment was extended to phenanthridone, the lactam of 6-hydroxyphenanthridine, which is a weak enough base in the ground and the excited states to require moderately concentrated mineral acids for protonation, and becomes a stronger base in the excited state than it is in the ground state. Phenanthridone exists as an -lactam and is a weaker base in the ground and excited states than the -lactams derived from 2-hydroxypyridine, 2-hydroxyquinoline, and 1-hydroxyisoquinoline. It is also a much weaker base than the vinylogous -lactams. The reasons for this are discussed here.