Alkylated lignin with graft copolymerization for enhancing toughness of PLA

Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then...     

Thiol-Functionalized Covalent Organic Frameworks as Thermal History Indictor for Temperature and Time History Monitoring

Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k_−20°C < k_4°C < k_20°C < k_35°C < k_55°C. The activation energy (E_a) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL⁻¹. The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs.     

Syntheses,structures and properties of cobalt and manganese complexes based on pyridine-2,3,5,6-tetracarboxylic acid

Two new complexes based on pyridine-2,3,5,6-tetracarboxylic acid(H₄pdtc) as ligand, {[Co₂(pdtc)(H₂O)₄] · H₂O}_n (1) and {Mn₂(pdtc)(H₂O)₄}_n (2), have been obtained by hydrothermal syntheses and characterized by IR, elemental analysis, X-ray diffraction single crystal structure analysis, PXRD, thermal gravimetric analysis, and magnetic measurements. Complex 1 is 3D coordination polymer and complex 2 belongs to 2D grid structure by covalent bonds. In 1 and 2, the metal ions show antiferromagnetic interactions.     

Facile synthesis of carbon self-doped g-C3N4 for enhanced photocatalytic hydrogen evolution

Graphite carbon nitride (g-C₃N₄) is an appealing metal-free photocatalyst for hydrogen evolution, but the potential has been limited by its poor visible-light absorption and unsatisfactory separation of photo-induced carriers. Herein, a facile one-pot strategy to fabricate carbon self-doped g-C₃N₄ composite through the calcination of dicyanamide and trace amounts of dimethylformamide is presented. The as-obtained carbon self-doped catalyst is investigated by X-ray photoelectron spectroscopy (XPS), confirming the substitution of carbon atoms in original sites of bridging nitrogen. We demonstrate that the as-prepared materials display remarkably improved visible-light absorption and optimized electronic structure under the premise of principally maintaining the tri-s-triazine based crystal framework and surface properties. Furthermore, the carbon doped g-C₃N₄ composite simultaneously weakens the transportation barrier of charge carriers, suppresses charge recombination and raises the separated efficiency of photoinduced holes and electrons on account of the extension of pi conjugated system. As a result, carbon self-doped g-C₃N₄ exhibits 4.3 times greater photocurrent density and 5.2 times higher hydrogen evolution rate compared with its bulk counterpart under visible light irradiation.     

纳米纤维素的疏水改性及应用研究进展

纳米纤维素作为一种性能优越的可再生纳米材料，应用前景极为广阔。然而，由于纳米纤维素结构上富含羟基，使其具有极强的亲水性，严重影响了纳米纤维素的疏水性能，并且在一定程度上限制了其在复合材料领域的应用。综述了纳米纤维素疏水改性的研究进展，从物理吸附、表面化学修饰（甲硅烷化、烷酰化、酯化等）、聚合物接枝共聚3个方面简述了目前应用较为广泛的疏水化改性方法，并对疏水纳米纤维素在包装材料、造纸、水净化等方面的应用现状进行了总结。最后对疏水改性纳米纤维素的未来发展进行了展望，旨在为疏水纳米纤维素的研究和应用提供参考。     

紫苏中迷迭香酸的乙醇提取优化实验研究

研究了采用乙醇提取法从紫苏中提取迷迭香酸的工艺条件。方法采用正交实验L9（3^4）优化迷迭香酸乙醇浸提法的提取工艺，硫酸亚铁比色法测定迷迭香酸含量。确定了最佳工艺条件为：50％乙醇为提取剂，料液比为1：50（w／v），提取温度为65℃，提取时间为35min，迷迭香酸提取率为1．061％比热水浸提法提高了30．18％。     

基于PowerBuilder的人事管理系统的设计与实现

随着计算机技术的飞速发展,计算机在企业管理中的应用得到普及,因此利用计算机实现高校人事管理势在必行。本文结合高校实际的人事制度,经过需求分析,采用功能强大的PowerBuilder 9.0作为开发工具和SQL Server 2000作为后台数据库,开发出高校人事管理系统。本文主要介绍系统的开发背景,要完成的功能和开发的过程,重点说明对系统的分析和设计,以及系统实现过程中的技术难点和解决方案。     

2011年12月计算机病毒疫情分析

根据国家计算机病毒应急处理中心对互联网的监测,2011年12月计算机病毒整体感染情况呈平稳态势,主要传播途径仍以＂网络钓鱼＂和＂网页挂马＂为主。     

“天河一号”大规模科学与工程计算应用

安装在国家超级计算天津中心(以下简称天津超算中心)的"天河一号"超级计算机系统是目前世界上最快的超级计算机,已广泛应用于多个高性能计算领域,并取得了一系列具有国际影响力的应用成果。本文主要介绍了"天河一号"在石油勘探数据处理、生物信息与生物医药、环境科学、工程仿真、磁约束聚变领域的最新应用成果,其成果表明"天河一号"在上述领域具有良好的可扩展性和并行效率,对自主科技创新和产业技术提升给予了巨大支撑。