Membrane disruption and DNA binding of Staphylococcus aureus cell induced by a novel antimicrobial peptide produced by Lactobacillus paracasei subsp. tolerans FX-6

Previously, we have isolated a novel bacteriocin, peptide F1 from Tibetan Kefir, and demonstrated its superior antimicrobial activity. However, its antimicrobial mechanism is still undefined. This study was aimed to elucidate the antimicrobial mechanism of peptide F1 against Staphylococcus aureus. The antimicrobial effects of peptide F1 were characterized by the following methods: chemical assay to quantify cytoplasmic β-galactosidase leakage, atomic absorption spectrometry to measure the released potassium ions, transmission electron microscopy to visualize the cellular morphological changes, and electrophoresis analysis and atomic force microscopy together to exam the DNA binding activity. Our results revealed that peptide F1 exerted its bactericidal effects by damaging bacterial cell membranes and by binding to the genomic DNA in the cytoplasm, which both led to rapid cell death.     

从空间管制角度谈对“多规合一”工作的思考

空间管制作为一种有效的空间资源配置和管理手段备受关注，也日益成为空间规划的重要内容和政府进行空间管理的重要抓手。要实现统一的空间管制，就必须进行“多规合一”。在“多规合一”的过程中，形成统一的控制线和空间管制分区，建立起“管制分区-责任主体-政策措施”三位一体的空间管制机制，并实现空间政策化，政策法制化。要实现管制空间与管制政策的协调，必须处理好技术理性与行政管理可操作性的关系，促使空间管制由技术性向政策性转型。完整的空间管制政策应包括三个部分，对管制分区的管理要求、实现管制目标的措施和空间开发权合理分配的保障机制。在明确分区管理控制性和约束性要求的同时，通过调节和补偿性政策措施，最终实现空间开发权的合理分配。     

Microstructure evolution and interfacial bonding mechanisms of ultrasonically soldered sapphire/Al dissimilar joints using Sn-based solders

Sapphire and 5A06 Al were ultrasonically soldered with Sn9Zn, SAC305 alloy solders and NiCu alloy foam added Sn-based composite solders, respectively. The microstructure and mechanical properties of joints were investigated and the interfacial bonding mechanism was analyzed. Cracks were observed at the sapphire/Sn matrix interface in joints soldered with alloy solders, which were disappeared in the joints soldered with composite solders. In the joint using NiCu–Sn9Zn composite solder, the solder seam was uneven and Al₃Ni intermetallic compound (IMC) layer was formed on the surface of NiCu alloy skeletons. While in the joint using NiCu-SAC305 composite solder, fine particles of (Ni,Zn)₃Sn₄ were largely formed and homogeneously distributed in the solder seam. An amorphous Al₂O₃ transition layer was formed at the sapphire/Sn matrix interface, and Zn enrichment was found at the Sn matrix/amorphous Al₂O₃ interface. The action mechanism of Zn was analyzed by first-principles calculation. The joints soldered with NiCu-SAC305 composite solder exhibited the highest shear strength of 74.42 MPa, the shearing failure mainly happened in the soldering seam.     

Effects of andalusite and kyanite addition on the microstructure,thermo-mechanical properties and corrosion resistance of ultralow-cement bauxite-corundum castables

Ultralow-cement bauxite-corundum refractory castables are increasingly attracting attention because of the advantages in performance and cost. To improve its volume stability and high-temperature performance, andalusite and kyanite were incorporated into this type of refractory, respectively, and a comparative investigation of their effects on microstructure, thermo-mechanical properties, and slag corrosion resistance was carried out in this work. The expansion effects induced by the mullitization of these additives not only suppressed the sintering shrinkage but also made the matrix structure more compact and uniform, mainly owing to the generation of many new and strong mullite bonds. This improvement resulted in a significant increase in the refractoriness under load and creep resistance. This effect was far more pronounced for the andalusite-added castables, for which the RUL increased by 62 °C and the creep rate at the stationary stage decreased by 26%. Besides, adverse effects on microstructure and properties appeared when adding a higher amount of kyanite due to the excessive expansion. Moreover, the corrosion mechanisms of these refractory castables by refining slag were discussed, and the active role of andalusite addition in the corrosion resistance was also proposed.     

新型建筑工业化的思考与对策

经过多年的曲折发展,我国建筑工业化已经步入了新的发展时期。认真研究新型建筑工业化的战略机遇,分析新型建筑工业化发展中存在的问题,思考加快推进新型建筑工业化发展的对策,具有重要的现实意义和长远的战略意义。在阐述推进新型建筑工业化发展的政策机遇的基础上,从政策扶持机制、设计技术体系、关键技术及集成技术、成本、舆论宣传和行业队伍水平6个侧面,剖析了推进新型建筑工业化发展过程中面临的困难和问题,有针对性地提出了加快推进新型建筑工业化发展的对策。     

Studies on pore blocking mechanism and technical feasibility of a hybrid PAC-MF process for reclamation of irrigation water from biotreated POME

An integrated low-cost adsorption (with powdered activated carbon, PAC) and cross-flow membrane filtration (with microfiltration membranes of 0.1 and 0.2 μm pore sizes) process was employed for the treatment of biotreated palm oil mill effluent (POME) to produce irrigation water that is fully benchmarked with water-quality standards. The permeate quality was within the recommended standard for irrigation water, as the concentrations of all critical constituents were well below their recommended values. Sustainability of the process integration was further confirmed with the domination of cake filtration over other blocking mechanisms with higher R² values at all trans-membrane pressures. Suitable extended usage of permeate was found for toilet/urinal flushing.     

A two-level self-adaptive variable neighborhood search algorithm for the prize-collecting vehicle routing problem

This paper investigates the prize-collecting vehicle routing problem (PCVRP), which has a strong background in practical industries. In the PCVRP, the capacities of all available vehicles are not sufficient to satisfy the demands of all customers. Consequently it is not a compulsory requirement that all customers should be visited. However, a prize can be collected once a customer is visited. In addition, it is required that the total demands of visited customers should reach a pre-specified value at least. The objective is to establish a schedule of vehicle routes so as to minimize the total transportation cost and at the same time maximize the prize collected by all vehicles. The total transportation cost consists of the total distance of vehicle routes and the sum of vehicles used in the schedule. To solve the PCVRP, a two-level self-adaptive variable neighborhood search (TLSAVNS) algorithm is developed according to the two levels of decisions in the PCVRP, namely the selection of customers to visit and the visiting sequence of selected customers in each vehicle route. The proposed TLSAVNS algorithm is self-adaptive because the neighborhoods and their search sequence are determined automatically by the algorithm itself based on the analysis of its search history. In addition, a graph extension method is adopted to obtain the lower bound for PCVRP by transforming the proposed mixed integer programming model of PCVRP into an equivalent traveling salesman problem (TSP) model, and the obtained lower bound is used to evaluate the proposed TLSAVNS algorithm. Computational results on benchmark problems show that the proposed TLSAVNS algorithm is efficient for PCVRP.     

可生物降解型聚氨酯的降解机理及研究进展

介绍了可生物降解型聚氨酯的概念、合成方式和降解性能表征方法以及降解机理,按可降解型聚氨酯发展4个阶段的顺序,综述了近年来国内外可生物降解型聚氨酯材料的研究进展,并指出了目前可降解型聚氨酯发展存在的问题和发展趋势。     

Effects of reaction parameters on generation of volatile compounds from the Maillard reaction between L‐ascorbic acid and glycine

The formation of volatiles from the reaction between L‐ascorbic acid (ASA) and glycine (Gly) at different reaction parameters, such as temperature, time and pH, were reported and 20 different volatile compounds were identified using solid‐phase microextraction–gas chromatography–mass spectrometry (SPME‐GC‐MS). The results showed that the reaction parameters had the different effects on formation of volatiles, while the effect of pH was the most remarkable. When the initial solution pH was 4.5, the major volatiles were found to be furfural or derivatives of furan; while when pH ranged from 6.8 to 9.5, the major volatiles were found to be derivatives of pyrazines, including 2,5‐dimethyl‐pyrazine, 2‐ethyl‐5‐methyl‐pyrazine, trimethyl‐pyrazine, 3‐ethyl‐2,5‐dimethyl‐pyrazine and 2,3‐diethyl‐5‐methyl‐pyrazine. The quantity of 2,5‐dimethyl‐pyrazine and 2‐ethyl‐5‐methyl‐pyrazine reached the maximum when pH was 8.0. Finally, a possible reaction mechanism of ASA and Gly and the pathway for the formation of the various kinds of volatile products were proposed.