直接模拟蒙特卡罗方法下的逆温度抽样算法

从分子动力学出发，讨论了直接模拟蒙特卡罗方法中分子平均总能量、平均平动能以及边界热流密度的抽样方法．通过对与边界发生碰撞的分子进行统计平均，得到了分子反射能量与入射能量以及边界热流密度的关系式．在此基础上，通过结合壁面漫反射模型下分子反射速度的抽样方法，发展了一种从边界热流求得与壁面碰撞分子的平均反射特征温度的逆温度抽样算法．数值结果表明：该算法能够由分子反射能量准确求得分子反射特征温度，进而求得分子反射速度，从而将边界热流信息带入流场．该方法为实现壁面处给定热流边界条件下的直接模拟蒙特卡罗方法提供了途径．     

超临界萃取荞麦中芦丁最佳工艺条件的研究

采用荞麦为实验原材料，比较系统地研究了在超临界状态下，样品含水量、萃取温度、压力、时间对萃取率的影响，确定最佳工艺条件，为批量生产提供依据。     

Theoretical study of electronic structure of rhodium mononitride and interpretation of experimental spectra

Potential energy curves of 22 electronic states of RhN have been calculated by the complete active space second‐order perturbation theory method. The X¹Σ₀⁺ is assigned as the ground state, and the first excited state a³Π₀+ is 978 cm^?1 higher. The ¹Δ(I) and B¹Σ⁺ states are located at 9521 and 13,046 cm^?1 above the ground state, respectively. The B¹Σ⁺ state should be the excited state located 12,300 cm^?1 above the ground state in the experimental study. Moreover, two excited states, C¹Π and b³Σ⁺, are found 14,963 and 15,082 cm^?1 above the X¹Σ⁺ state, respectively. The transition C¹Π₁–X¹Σ₀⁺ may contribute to the experimentally observed bands headed at 15,071 cm^?1. There are two excited states, D¹Δ and E¹Σ⁺, situate at 20,715 and 23,145 cm^?1 above the X¹Σ⁺ state. The visible bands near 20,000 cm^?1 could be generated by the electronic transitions D¹Δ₂–a³Π₁ and E¹Σ⁺₀–X¹Σ⁺₀ because of the spin–orbit coupling effect. © 2013 Wiley Periodicals, Inc.     

Mechanism and Cellular Kinetic Studies of the Enhancement of Antioxidant Activity by Using Surface‐Functionalized Gold Nanoparticles

The enhanced antioxidant activity of surface‐functionalized gold nanoparticles (AuNPs) synthesized by self‐assembly has attracted great attention, but little is known about the mechanism behind the enhanced activity. To address this challenge, the antioxidant activity of Au@PEG3SA (i.e., surface‐functionalization of spherical AuNPs with the antioxidant salvianic acid A) was used as an example to illustrate the mechanism of the enhanced activity. Evaluation of the antioxidant activity was performed in a radical‐scavenging reaction between Au@PEG3SA and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical. As expected, the rate constant for the reaction of Au@PEG3SA with DPPH was about nine times greater than that for the salvianic acid A monomer. A comparative analysis of the spectral characteristics of Au@PEG3SA and the salvianic acid A monomer further imply that the enhancement of the antioxidative reaction kinetics may be ascribed to the variation in the transition state for the DPPH‐radical scavenging reaction through π–π stacking interactions between and among adjacent groups on the surface of Au@PEG3SA. On the other hand, the kinetic enhancement of Au@PEG3SA on reactive‐oxygen‐species (ROS) scavenging can be observed in living cells and in vivo, which possibly provides new insight for the bioapplication of self‐assembly of surface‐functionalized AuNPs.     

Extraction of coal-tar pitch using NMP/ILs mixed solvents

Coal-tar pitch(CP)is a promising carbon raw material for producing needle coke,carbon fiber etc.During processing,the H/C ratio,ash content,and quinoline insoluble(QI)in the CP are the key factors that influence the material preparation.In this study,NMP was selected to extract CP first;then[BMIM]Cl/NMP mixed solvent was used;and finally a series of ionic liquids(ILs)mixtures with NMP were developed for the extraction of CP to obtain the refined pitch.The extracts were analyzed via elemental analysis,TGA,FT-IR,and 13C-NMR.Results indicate that different NMP/IL mass ratios or different kinds of ILs have impact on the extraction yield.The relationship of the hydrogen to carbon(H/C)ratio changed with different solvents and QI extracts were obtained.Results showed that the H/C ratios changed little between NMP extracts and could be adjusted by changing the NMP/ILs mass ratio or using different ILs.The extracts are suitable for preparation mesophase pitch because of no ash content,low QI,and appropriate H/C ratios.As a result,NMP can be used to refine pitch.In addition,[BMIM]Cl is good mixed with NMP for CP extraction,because it can obtain a relatively high yield under the same extraction conditions.     

Water-in-salt widens the electrochemical stability window: Thermodynamic and kinetic factors

Originating from the 1.23 V potential window of pure water, the narrow electrochemical stability window (ESW) has always been the most stubborn problem for aqueous battery systems. However, the water-in-salt system magically widens the ESW of aqueous electrolyte from 1.23 V to above 3 V by the super-concentrated LiTFSI solution. The mechanisms of widening aqueous battery ESW have been a crucial topic, in which the significant factors, including unique solid–electrolyte interface, solvation structure, and others, have been highlighted. Here, we specify the concept of ESW in detail and review the influence factors of ESW in the water-in-salt system from both thermodynamic and kinetic perspectives to explore the importance of each factor.     

Hyperterpenoids A and B: Two pairs of unprecedented 6/6/4/6/6 polycyclic cyclobutane meroterpenoids with potent neuroprotective and anti-inflammatory activities from Hypericum beanii

Hyperterpenoid A (1) and B (2), two pairs of enantiomers, with an unprecedented 6/6/4/6/6 polycyclic skeleton, along with one known compoud hypermonone A (3) were isolated from Hypericum beanii. The racemate (±)-1 and (±)-2 were successfully separated into the two optically pure enantiomers (ee ≥ 99%) using a preparative HPLC system. Their absolute configurations were elucidated by extensive spectroscopic analyses and single-crystal X-ray diffraction method. The related plausible biogenetic pathways were presented. Compound 1-3 showed significant neuroprotective activity and potential anti-inflammatory activity. The result that (+)-2 and (-)-2 presented different anti-inflammatory properties, may lead us to new discovery of structure activity relationship between racemates, enantiomers, and diastereomers, as well as further research regarding the binding of drugs to target proteins.     

硫化铟锌的改性合成及光催化特性

随着社会经济的高速发展,能源的短缺和生态的破坏引起了人们的关注。近年来,寻找合适的解决方案已成为关注的重点。作为一种绿色环保技术,光催化由于其高效、低成本等优点而成为能源和环境问题的研究热点。在许多光催化材料中,三元硫化物硫化铟锌(ZnIn₂S₄)由于具有可见光响应特性、简单的制备方法和出色的稳定性而表现出巨大的潜力。然而,较高的载流子复合率限制了其光催化性能。近年来,许多研究报道了改性ZnIn₂S₄以提高其光催化性能,在此,本文详细介绍了各种改性研究,包括ZnIn₂S₄单体的合成、半导体化合物的结构、贵金属沉积、碳元素改性、离子掺杂。然后,系统完整地总结了ZnIn₂S₄在光催化、降解有机污染物、去除六价铬、还原CO₂和有机合成等方面表现出的光催化特性和机理。最后,对ZnIn₂S₄的发展前景提出了展望,以期ZnIn₂S₄光催化剂得到更广泛和深入的研究,尽快在实际生产中得到应用。