An interlocked coordination cage based on aromatic amide ligands

An interlocked M_4 L_8 coordination cage was synthesized by coordination-driven self-assembly of palladium(Ⅱ) ions with aromatic amide bidentate ligands.The reaction of the ligand and the metal at 2:1 ratio led to the monomeric M_2 L_4 cage as the kinetic product,while the thermodynamic product M_4 L_8 cage was obtained by prolongating the reaction.This conve rsion and the interlocked structure was clearly revealed by using ~1 H NMR,mass spectrometry and X-ray crystallography.The driving force of interlocking was mainly attributed to the interactions(hydrogen bonding,aromatic stacking and electrostatic interaction) arising from the aptitude of flexibility of the amide ligand.     

Structure-based design,synthesis of novel probes for cytochrome P450 OleT

Cytochrome P450 OleT_SA, a new cytochrome P450 enzyme from Staphylococcus aureus, catalyzes the oxidative decarboxylation and hydroxylation of fatty acids to generate terminal alkenes and fatty alcohols. The mechanism of this bifurcative chemistry remains largely unknown. Herein, a class of derivatized fatty acids were synthesized as probes to investigate the effects of substrate structure on the product type of P450 OleT_SA. The results demonstrate that the fine-tuned structure of substrates, even in a remote distance from the carboxyl group, significantly regulates OleT catalyzed decarboxylation/hydroxylation reactions. Molecular docking analysis indicated the potential interactions between the carboxylate groups of different probes and the enzyme active center which was attributed to the bifurcative chemistry.     

ZIF-derived mesoporous carbon materials prepared by activation via Na2SiO3 for supercapacitor

Metal organic frameworks (MOFs) derived carbonaceous materials have a wide range of applications in the fields of energy storage, catalysis, adsorption and separation, etc. Especially, zeolitic imidazolate framework-8 (ZIF-8) is an excellent candidate to synthesize porous carbon due to the large surface area and high nitrogen content. However, the dominated microporous structure of ZIF-8-derived carbon significantly hinders ionic mass transfer, limiting the improvement of performance. Herein, MOF-derived mesoporous carbon was prepared using ZIF-8 as carbon precursor and cheap sodium silicate (Na₂SiO₃) as activator. The introduction of Na₂SiO₃ created rich mesoporous structure and increased specific surface area, as well as the effects of pyrolysis temperature and Na₂SiO₃ dosage on performance was also investigated. The obtained ZIF-derived porous carbon exhibits good electrochemical performance with specific capacitance of 263 F/g at 1 A/g and excellent cycle life (96.07% after 10,000 GCD cycles) in supercapacitor. The use of cheap Na₂SiO₃ activator provides a new orientation for the preparation of MOF-derived carbons with rich pores, high surface area, and facilitates the large-scale application of MOF-derived carbons.     

Imaging the Magnetic Reversal of Isolated and Organized Molecular‐Based Nanoparticles using Magnetic Force Microscopy

In the race towards miniaturization in nanoelectronics, magnetic nanoparticles (MNPs) have emerged as potential candidates for their integration in ultrahigh‐density recording media. Molecular‐based materials open the possibility to design new tailor‐made MNPs with variable composition and sizes, which benefit from the intrinsic properties of these materials. Before their implementation in real devices is reached, a precise organization on surfaces and a reliable characterization and manipulation of their individual magnetic behavior are required. In this paper, it is demonstrated how molecular‐based MNPs are accurately organized on surfaces and how the magnetic properties of the individual MNPs are detected and tuned by means of low‐temperature magnetic force microscopy (LT‐MFM) with variable magnetic field. The magnetization reversal on isolated and organized MNPs is investigated; in addition, the temperature dependence of their magnetic response is evaluated.     

装备使用与保障研究数据的生成方法研究

装备使用与保障数据是开展装备科学研究的重要依据,而由于管理不善、保密、样本过少等原因常常导致相关数据缺少应有的积累,无法满足实际研究的需要。为了克服这一困难,文章提出通过算法生成数据予以解决。首先根据数据的应用特性,将装备使用与保障数据看作简单数据、规律已知数据和规律未知数据三类,分别制定生成策略。对于简单数据和规律已知数据,通过已有的商用软件或简单的自定义方法生成;对于规律未知数据,采用模式注入或特性继承的方法生成。在某大型装备管理综合信息系统的设计开发中,对这些生成方法进行了工程实践,结果表明了方法的正确性和可行性。     

基于WIA-PA传感器网络的能量有效时间同步算法

WIA-PA协议是一种新型工业级无线传感器网络国际标准。当WIA-PA网络内节点数目增多时,传统的参考广播同步算法RBS以及改进型ERBS算法网络开销非常大。针对这一严峻的问题,提出了一种能量有效的局部最优时间同步算法。该算法对相邻的接收节点在多个参考广播消息的条件下求取平均相位偏差,然后对此平均相位偏差进行最大后验估计,最后根据此估计值调整本地时钟。仿真结果表明,本文所提时间同步算法在同步精度方面比RBS约提高168%,比ERBS约提高24%;同时,同步过程中的网络能耗也大大减少。     

微液滴在不同能量表面上润湿状态的分子动力学模拟

微小液滴在不同能量表面上的润湿状态对于准确预测非均相核化速率和揭示界面效应影响液滴增长微观机理具有重要意义. 通过分子动力学模拟, 研究了纳米级液滴在不同能量表面上的铺展过程和润湿形态. 结果表明, 固液界面自由能随固液作用强度增加而增加, 并呈现不同液滴铺展速率和润湿特性. 固液作用强度小于1.6的低能表面呈现疏水特征, 继续增强固液作用强度时表面变为亲水, 而固液作用强度大于3.5的高能表面上液体呈完全润湿特征. 受微尺度条件下非连续、非对称作用力影响, 微液滴气液界面存在明显波动, 呈现与宏观液滴不同的界面特征. 统计意义下, 微小液滴在不同能量表面上铺展后仍可以形成特定接触角, 该接触角随固液作用强度增加而线性减小, 模拟结果与经典润湿理论计算获得的结果呈现相似变化趋势. 模拟结果从分子尺度为核化理论中的毛细假设提供了理论支持, 揭示了液滴气液界面和接触角的波动现象, 为核化速率理论预测结果和实验测定结果之间的差异提供了定性解释.     

冷凝法甲苯回收系统性能研究与优化

基于已有典型工业挥发性有机物甲苯设计的一套冷凝法回收系统,对其进行数值模拟和优化设计。运用物性软件REFPROP对甲苯负荷及制冷系统性能进行了模拟。通过对系统的模拟计算,研究了冷却级蒸发温度、冷凝温度以及甲苯混合气体入口温度对该冷凝法甲苯回收系统的性能影响,并针对冷却级温度影响进行了经济性分析。在此基础上,提出了冷量回收的优化方案,并与原有方案进行了对比分析,为进一步优化设计提供了理论依据。优化结果表明:系统预冷级负荷降低69.6%,系统的能耗降低38.9%,COP增大61.4%,压缩机排气温度下降7.7℃。