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51.
为探索生物活性未知的双对苯醌(2,7-dihydroxy-3,6,9-trimethyl-9H-xanthene-1,4,5,8-tetraone,DTXT)的抗氧化活性,并提高其发酵产量,考察DTXT的还原力以及对超氧阴离子自由基、羟自由基、1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基的清除效果,在单因素试验基础上,采用响应面法优化了DTXT产生菌瓶生顶孢霉(Acremonium cavaraeanum)CA022菌株的固体发酵培养基。结果表明:在200 μg/mL质量浓度下,DTXT的还原力与芦丁差异不显著,高于VE和2,6-二叔丁基-4甲基苯酚,对超氧阴离子自由基清除率达到67.00%,对羟自由基清除率达到78.83%,对DPPH自由基清除率达到76.53%。通过响应面试验,得到最佳培养基配方为葡萄糖0.773%、硝酸钠0.185%、H3BO3 0.032%、VB1 100 μg/100 g,在此条件下实际获得的DTXT产量为4 150.8 mg/kg,是优化前产量的(2 864.83 mg/kg)1.45 倍。 相似文献
52.
Properties of polyamide 6,10/poly(vinyl alcohol) blends and impact on oxygen barrier performance 下载免费PDF全文
Jia‐wei Wu Ya‐qiong Huang Hong‐bo Li James Runt Jen‐taut Yeh 《Polymer International》2018,67(4):453-462
The oxygen transmission rate, average volume of free‐volume cavities (Vf) and fractional free volume (Fv) of polyamide 6,10 (PA610)/poly(vinyl alcohol) (PVA) (i.e. PA610xPVA05y, PA610xPVA08y and PA610xPVA14y) blend films reduced to minimum values when their PVA contents reached corresponding optimal values. Oxygen transmission rate, Vf and Fv values obtained for optimal PA610xPVAzy blown films were reduced considerably with decreasing PVA degrees of polymerization. The oxygen transmission rate of the optimal bio‐based PA61080PVA0520 blown film was only 2.4 cm3 (m2·day·atm)?1, which is about the same as that of the most often used high‐barrier polymer, ethylene–vinyl alcohol copolymer. Experimental findings from dynamic mechanical analysis, differential scanning calorimetry, wide‐angle X‐ray diffraction and Fourier transform infrared spectroscopy of the PA610xPVAzy blends indicate that PA610 and PVA in the blends are miscible to some extent at the molecular level when the PVA contents are less than or equal to the corresponding optimal values. The considerably enhanced oxygen barrier properties of the PA610xPVAzy blend films with optimized compositions are attributed to the significantly reduced local free‐volume characteristics. © 2017 Society of Chemical Industry 相似文献
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Martin G. Bakker Benjamin Fowler Michael K. Bowman Gregory S. Patience 《加拿大化工杂志》2020,98(8):1668-1681
Electron paramagnetic resonance (EPR) spectroscopy, also known as electron spin resonance spectroscopy (ESR), utilizes absorption of microwave radiation by unpaired electrons in a magnetic field. The interaction between the unpaired electron(s) and nearby magnetic nuclei helps identify paramagnetic species and can provide information about the motion of the molecule and the local polarity, pH, viscosity, concentration, and accessibility to other paramagnetic species. This mini-review discusses the fundamental underpinnings of EPR needed to correctly interpret EPR spectra. We describe various types of EPR spectra encountered by chemical engineers, and use application examples drawn from the chemical engineering literature to illustrate the information available from the technique. Few chemical engineering departments or even chemistry departments have EPR instruments, which contributes to the significant barrier that prevents this being adopted as a routine measurement technique. However, in 2016 and 2017, Web of Science indexed 7000 articles that applied EPR spectroscopy. A bibliometric map categorized the keywords in four categories based on co-occurrences: magnetic properties, films, and luminescence; crystal structure, complexes, and ligands; nanoparticles, oxidation, and degradation; and, systems, radicals, and H2 O2 . 相似文献
55.
《International Journal of Hydrogen Energy》2020,45(46):25426-25437
The fuel mixing process within the combustion chamber is a critical procedure for advance of scramjet engine. In current study, the influence of free stream angle on the fuel mixing process of multi jets was thoroughly investigated. This research attempts to applied computational technique to disclose the structure of multi-fuel jets when the supersonic air stream is not normal to the jet direction. The effect of both positive and negative supersonic free stream on the diffusion and penetration of multi-hydrogen jets is fully described. The attention of this research is the flow structure of the multi jets and their interaction in the presence of different free stream angle. Our results indicate that the positive free stream angle expands the mixing zone in the downstream while the negative angle of free stream limited jet distribution inside the combustor. Our results show that mixing efficiency increase approximately 50% when the angle of free stream augments from +20° to −20°. According to our findings, mixing efficiency surges up to 17% when the jet spaces are increased from 4Dj to 10 Dj. 相似文献
56.
某高硫难处理金精矿超细磨提金试验研究 总被引:1,自引:1,他引:0
针对某高硫难处理金精矿中金大部分被黄铁矿包裹、直接氰化浸出金浸出率低的问题,采用超细磨-碱预处理-氰化浸出工艺处理金精矿,通过条件优化可获得金浸出率84.50%,氰化钠耗量控制在3 kg/t以内,该工艺简单、流程短、安全环保。 相似文献
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58.
为了研制一种具有荧光功能特性的高固低黏羟基丙烯酸树脂。从聚集诱导发光效应(AIE)出发,将具有 AIE性质的二对丙烯酸四苯乙烯酯荧光分子通过自由基共聚连接于聚合物链段。由于聚合物链段对荧光分子化学键固定以及聚合物链的包裹束缚作用,导致荧光分子运动受限,从而实现涂层在紫外灯下荧光发光。通过荧光光谱的实时跟踪,探索高固低黏羟基丙烯酸树脂的合成以及固化规律。此外,由于聚合物链段对外界刺激具有实时响应性,从而间接影响了所连接的荧光分子的荧光发光行为。因此,文中也探索了涂层在外界温度与化学气体的影响下所发生的荧光变化的规律,以探索其在功能涂层中应用的可行性。 相似文献
59.
《International Journal of Hydrogen Energy》2020,45(7):4174-4181
The concept of thermochemical exhaust heat recuperation by steam reforming of biofuels is considered. Thermochemical recuperation can be considered as an on-board hydrogen production technology. A schematic diagram of a fuel-consuming equipment with thermochemical heat recuperation is described. The thermodynamic analysis of the thermochemical recuperation systems was performed to determine the efficiency of using various fuels, in particular, methanol, ethanol, n-butanol, and glycerol. The thermodynamic analysis was performed by Gibbs free energy minimization method and implemented using the Aspen Hysys program. The thermodynamic analysis was performed for a wide temperature range from 400 to 900 K, for steam-to-fuel of 1, and pressures of 1 bar. The maximum fuel conversion reaches for the following temperatures: methanol - 600 K, ethanol - 730 K, n-butanol - 860 K, glycerol - 890 K. The dependence of the reforming enthalpy on temperature is determined. It was shown that the reaction enthalpy determines the heat transformation coefficient, which shows the ratio of the low heat value of synthetic fuel and the low heat value of the initial fuel. For all studied fuels, the maximum value of the transformation coefficient is observed for steam reforming of ethanol and the maximum heat transformation coefficient is 1.187. The temperature range is determined at which the maximum efficiency of the use of thermochemical recuperation occurs due to the reforming of biofuels. For methanol, the effective temperature is about 600 K, for ethanol is about 700 K, for n-butanol is 850 K, for glycerol is more than 900 K. The results obtained make it possible to efficiently select the type of fuel for thermochemical recuperation due to steam reforming. 相似文献
60.