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排序方式: 共有1762条查询结果,搜索用时 11 毫秒
61.
J. Saúl García-Pérez Sara P. Cuéllar-Bermúdez Alejandra Arévalo-Gallegos José Rodríguez-Rodríguez Hafiz M. N. Iqbal Roberto Parra-Saldivar 《International journal of molecular sciences》2016,17(9)
Supercritical fluid extraction (SFE) is a sustainable technique used for the extraction of lipophilic metabolites such as pigments and fatty acids. Arnica plant is considered a potential candidate material with high antioxidant and antimicrobial activities. Therefore, in this study, a locally available Heterotheca inuloides, also known as Mexican arnica, was analyzed for the extraction of high-value compounds. Based on different pressure (P), temperature (T), and co-solvent (CoS), four treatments (T) were prepared. A maximum 7.13% yield was recovered from T2 (T = 60 °C, P = 10 MPa, CoS = 8 g/min), followed by 6.69% from T4 (T = 60 °C, P = 30 MPa, CoS = 4 g/min). Some bioactive sesquiterpenoids such as 7-hydroxycadalene, caryophyllene and δ-cadinene were identified in the extracts by GC/MS. The fatty acid profile revealed that the main components were palmitic acid (C16:0), followed by linoleic acid (C18:2ω6c), α-linolenic acid (C18:3ω3) and stearic acid (C18:0) differing in percent yield per treatment. Antibacterial activities were determined by the agar diffusion method, indicating that all the treatments exerted strong antibacterial activity against S. aureus, C. albicans, and E. coli strains. The antioxidant capacity of the extracts was also measured by three in vitro assays, DPPH, TEAC and FRAP, using Trolox as a standard. Results showed high antioxidant capacity enabling pharmaceutical applications of Mexican arnica. 相似文献
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线材的氧化铁皮起着保护线材免锈蚀的作用,但是也需要在酸洗时容易除去。影响铁皮除去或结合力的主要是铁皮的厚度和其物相结构。通过对不同轧制条件下的氧化铁皮厚度、物相结构进行检测分析,研究了精轧温度和吐丝温度对φ12 mm SCM435氧化铁皮物相结构的影响。研究表明,随着精轧温度或吐丝温度的升高,SCM435线材的氧化铁皮厚度均会增加,且在800-900℃短时间就会生成较厚(约20μm)的氧化铁皮;由于Cr的氧化选择性,精轧温度在870℃以上,吐丝温度在810℃以上时,随精轧温度或吐丝温度升高,氧化铁皮中FeO比例提高;但是吐丝温度高于860℃后,物相结构的变化趋缓,FeO的比例变化不大。 相似文献
64.
三山岛西岭金矿区位于渤海之滨,与北部海域金矿区相互连接,形成金资源量近千吨的巨型金矿床,矿床为地下与海底开采。区域内断裂发育,分布有NE向和NW向断裂,其中NE向断裂为控矿构造,而NW向断裂多具有不同程度的导水性,对矿床安全开采影响重大。基于矿区地质条件与地球物理特征,采用高精度磁测法和音频大地电磁(AMT)法在矿区东部进行了勘查试验,根据显示的磁性异常与电性异常,在平面上解译了NW向断裂(F-1、F-2)与NE向断裂(F-3、F-4),在L1剖面上解译了4条断裂,在L2剖面上解译了3条断裂。综合判断解译信息,NW向F-1断裂在平面与剖面上都反映良好。同时,与北部海域NW向构造研究资料进行对比分析,结果显示西岭矿区F-1推断断层与北部海域B-F4断层特征一致,吻合较好,推断西岭矿区NW向F-2断裂被F-3断裂错断。研究结果说明综合物探方法在该区域可行有效,为下一步钻孔验证NW向断裂存在,判断断裂富水及导水性质,以及未来矿床开发利用提供了地球物理依据。 相似文献
65.
To explore the crucial driving forces and dynamics of the Chinese apparel industry cluster, the authors analysed current situations, characteristics and the dilemma in the Chinese apparel industry based on surveys conducted in the Yangtze River Delta. This study classified the factors impacting apparel industry cluster development into necessary conditions and evolutionary factors according to logistic differential equation, and proposed a dynamics model framework of apparel industry cluster with positive and negative feedback mechanism. The authors believe that the Chinese apparel industry cluster is an ecology system involving outsourcing, specialisation agglomerating, competition, resource complementary, etc. and has a quick response ability of adapting to environment. 相似文献
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阳离子石蜡乳液的制备及其在中性施胶和表面涂饰中的应用 总被引:12,自引:1,他引:12
石蜡乳液是一类重要的中性施胶剂,但一直存在难乳化,乳液稳定性差,单独进行中性施胶时效果差等问题,我们探讨了各种因素对石蜡乳液稳定性和应用性的影响,制备出一种稳定且具有良好中性施胶性能的阳离子石蜡乳液,确定了其最佳施胶工艺。 相似文献
69.
Surface grafting of carbon fibers with artificial silver‐nanoparticle‐decorated graphene oxide for high‐speed electrical actuation of shape‐memory polymers
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Poor heat conduction in the interface between the carbon fiber and polymer matrix is a problem in the actuation of shape‐memory polymer (SMP) composites by Joule heating. In this study, we investigated the effectiveness of grafting silver‐nanoparticle‐decorated graphene oxide (GO) onto carbon fibers to improve the electrothermal properties and Joule‐heating‐activated shape recovery of SMP composites. Self‐assembled GO was grafted onto carbon fibers to enhance the bonding of the carbon fibers with the polymeric matrix via van der Waal's forces and covalent crosslinking, respectively. Silver nanoparticles were further self‐assembled and deposited to decorate the GO assembly, which was used to decrease the thermal dissimilarity and facilitate heat transfer from the carbon fiber to the polymer matrix. The carbon fiber was incorporated with SMP to achieve the shape recovery induced by Joule heating. We found that the silver‐nanoparticle‐decorated GO helped us achieve a more uniform temperature distribution in the SMP composites compared to those without decoration. Furthermore, the shape‐recovery behavior and temperature profile during the Joule heating of the SMP composites were characterized and compared. A unique synergistic effect of the carbon fibers and silver‐nanoparticle‐decorated GO was achieved to enhance the heat transfer and a higher speed of actuation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41673. 相似文献
70.
污水处理是一个复杂的非线性过程,化学需氧量(chemical oxygen demand,COD)是评价污水处理效果的关键指标之一。COD的传统测量方法耗时长、成本高,基于传统神经网络的软测量方法提高了COD参数的测量速度但精度较差。针对这些问题,设计一种结合自组织特征映射 (self-organizing map, SOM)和径向基函数(radial basis function, RBF)神经网络的COD参数软测量方法。该方法利用SOM网络聚类数据样本,根据所得聚类结果确定RBF网络的隐层节点数及节点的数据中心,综合提高RBF网络的收敛速度和拟合精度。利用污水处理厂部分水样数据建立COD软测量模型,模型仿真和硬件在线测试结果表明,相对于传统的BP、RBF等网络,基于SOM-RBF神经网络的COD软测量方法测量时间短、预测精度较高,具有较为广阔的应用前景。 相似文献