Essential oil composition and antimicrobial activity of Sphallerocarpus gracilis seeds against selected food-related bacteria

Sphallerocarpus gracilis from China is a little-investigated edible and medicinal plant. In the present study, the essential oil composition from S. gracilis seeds was investigated by GC and GC–MS. A total of 34 compounds representing 94.69% of the essential oil were tentatively identified. The main constituents were p-cymene (17.42%), γ-terpinene (25.58%) and α-asarone (33.12%). The antimicrobial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of the essential oil from S. gracilis seeds were evaluated against eight Gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Bacillus megaterium, Bacillus cereus, Bacillus coagulans and Bacillus subtilis), four Gram-negative bacteria (Salmonella enteritidis, Salmonella typhimurium, Klebsiella pneumoniae and Escherichia coli) and one fungus (Aspergillus niger). Results revealed that the essential oil from S. gracilis seeds exhibited significant in vitro antimicrobial property. Among all the tested microorganisms, the essential oil showed the strongest inhibitory effect against K. pneumoniae, whereas no inhibitory effect was found against L. monocytogenes and A. niger. Additionally, scanning electron microscopy (SEM) was used to observe morphological changes of bacteria treated with the essential oil from S. gracilis seeds. SEM observations confirmed the physical damage and considerable morphological alteration to the tested microorganisms treated with the essential oil. The data of this study suggests that the essential oil from S. gracilis seeds has great potential for application as a natural antimicrobial agent to preserve food.     

我国企业网络数据库营销策略研究

随着信息技术的发展,网络数据库营销的应用越来越广泛.网络数据库是网络数据库营销的技术基础,它为企业实施网络数据库营销提供了技术支持.我国企业在实施网络数据库营销的过程中还存在着许多问题,要以合理的对策加以解决,才能促进我国企业网络数据库营销的开展.     

The Dependence of Energy Dissipation on the Elastic Energy Density of Friction Pairs in Hard Coating Films

The influence of different pairs on the energy dissipation of a given hard coating during fretting has been discussed. Based on the view of the competition between the elastic and plastic deformations in a fretting experiment, it suggests that the energy dissipation rate is proportional to the elastic energy density of pairs. This trend is in agreement with the reported experimental data. For comparison, hardness of pairs is used as the index to relate the antiwear properties of a DLC film against different pairs. It is obvious that the elastic energy density of pairs is more appropriate to predict the antiwear properties of the DLC film against different pairs.     

Fretting wear behavior of bulk amorphous steel

Fretting wear of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ bulk metallic glass (BMG) was investigated using the ball-on-disc measurement. The wear behaviors of the samples roughly follow the classical Archard wear law at room temperature. The influence of temperature on wear resistance (R_w) and microhardness (H_v) was evaluated. A good linear correlation was found between R_w and H for the Fe-based BMG. The results indicate that the hardness softening is responsible for the decrease of R_w at high temperature. The wear mechanism at high temperature was elucidated through the analysis of oxidation and debris morphology on the wear scar. Compared with traditional crystalline steels and other non-ferrous metal-based glassy alloys, the bulk amorphous steel shows higher wear resistance and hardness, which promotes its application as an advanced engineering material.     

On the formalization and reuse of scientific research

The reuse of scientific knowledge obtained from one investigation in another investigation is basic to the advance of science. Scientific investigations should therefore be recorded in ways that promote the reuse of the knowledge they generate. The use of logical formalisms to describe scientific knowledge has potential advantages in facilitating such reuse. Here, we propose a formal framework for using logical formalisms to promote reuse. We demonstrate the utility of this framework by using it in a worked example from biology: demonstrating cycles of investigation formalization [F] and reuse [R] to generate new knowledge. We first used logic to formally describe a Robot scientist investigation into yeast (Saccharomyces cerevisiae) functional genomics [f₁]. With Robot scientists, unlike human scientists, the production of comprehensive metadata about their investigations is a natural by-product of the way they work. We then demonstrated how this formalism enabled the reuse of the research in investigating yeast phenotypes [r₁ = R(f₁)]. This investigation found that the removal of non-essential enzymes generally resulted in enhanced growth. The phenotype investigation was then formally described using the same logical formalism as the functional genomics investigation [f₂ = F(r₁)]. We then demonstrated how this formalism enabled the reuse of the phenotype investigation to investigate yeast systems-biology modelling [r₂ = R(f₂)]. This investigation found that yeast flux-balance analysis models fail to predict the observed changes in growth. Finally, the systems biology investigation was formalized for reuse in future investigations [f₃ = F(r₂)]. These cycles of reuse are a model for the general reuse of scientific knowledge.     

Mechanically strong conducting hydrogels with special double-network structure

Mechanically strong conducting hydrogels composed of poly(acrylamide) (PAAm) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) have been synthesized through the construction of a special double-network (sDN) structure. The novelty of the sDN hydrogels lies in the introduction of PEDOT-PSS semi-interpenetrating polymer network (semi-IPN) hydrogel as the second network. Based on the experimental results and the double-network theory, an additional strengthening effect resulting from the formation of the PEDOT clusters in a three-step fracture process is proposed. The applicability of as-prepared PAAm/PEDOT-PSS sDN hydrogels in electromechanical actuators is also briefly discussed.     

柴油降凝剂的发展现状及其研究热点

综述了梳状聚合物型、烯-不饱和酯聚合物型、酰胺酸盐共聚物型、烷基芳烃型和聚丙烯酸高碳醇酯型等几种柴油降凝剂近年来在合成方面的研究进展,重点讨论了目前的研究热点,展望了其今后的发展方向。     

温敏型有机-无机杂化纳米微胶囊的渗透性能

将N-异丙基丙烯酰胺引入以正十六烷为模板的苯乙烯与甲基丙烯酸-3-三甲氧基硅丙酯细乳液共聚法制备纳米微胶囊的体系,得到一种温敏型有机-无机杂化纳米微胶囊。采用紫外可见分光光度计研究该种微胶囊在临界温度附近对甲酚红的载入和释放行为。结果表明N-异丙基丙烯酰胺的引入和温度均影响纳米微胶囊对甲酚红的载入与释放。微胶囊在临界温度以上具有一定渗透速率,临界温度以下渗透不明显,能较好地实现开-关式环境温敏型控制吸附和释放。