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991.
Armeniaca mume Sieb. blossom is among the traditional Chinese edible flowers, and it is widely used in the food and pharmaceutical industries. Flavonoids are among the most abundant bioactive compounds in A. mume Sieb. blossom. However, the research on the extraction of flavonoids from A. mume Sieb. blossom and their immunomodulating function is insufficient. In this study, we developed a microwave-assisted enzymatic extraction of flavonoids from A. mume Sieb. blossom (FAMB) and explored their immunomodulating effect on mice with dextran sulfate sodium salt-induced colitis. The results showed that the optimum parameters for microwave-assisted enzymatic extraction of FAMB were as follows: cellulase: 2.0%; microwave power: 200 W; microwave action time: 5 min; and enzymatic hydrolysis time: 50 min. FAMB significantly promoted the lymphocyte proliferation and natural killer (NK) cell killing activity in colitis mice, and increased the concentrations of TNF-α, IFN-γ, and IL-2 in serum. FAMB also significantly reduced the apoptosis of spleen lymphocytes in these mice. These results demonstrated that the microwave-assisted enzymatic method could significantly improve the yield and efficacy extraction of FAMB. FAMB showed a good immunomodulation effect on colitis mice. 相似文献
992.
Yue Wang Jinping Wu Tian Yang Zhong Wang Yasushi Hasebe Tianhang Lv Zhiqiang Zhang 《Electroanalysis》2021,33(12):2445-2451
An ascorbic acid (AA) electrochemical sensor was fabricated by ferrocene methanol (Fc−OH) modified multi-walled carbon nanotube yarn (CNTY). The prepared sensor (Fc−OH/CNTY) exhibited outstanding flexibility, highly stretchability, excellent bendability and obviously electrocatalytic activity for oxidation of ascorbic acid. The morphology of Fc−OH/CNTY was evaluated by scanning electron microscope. The electrochemical behaviour of Fc−OH/CNTY sensor was studied by cyclic voltammetry and amperometry measurements. Moreover, the influence of Fc−OH concentration, applied potential and electrolyte solution pH were also investigated to obtain the best sensor performance. The prepared sensor exhibited a wide linear range from 3 μM to 3.0 mM toward AA, and a detection limit of 1.32 μM (S/N=3). It also possessed a good lifetime and a fast response speed (2.83 s). In addition, the Fc−OH/CNTY sensor remained 90 % and 60 % of its initial activity after 100 and 500 times bending, respectively, which indicated a potential application on flexible, implantable and/or wearable electrochemical sensors. 相似文献
993.
氢气具有无毒、能量密度高以及燃烧过程零污染等优点,被誉为是未来代替化石能源的优质新型能源载体.探索高效的、可持续的制氢技术对氢气能源发展至关重要.其中,光电化学水分解电池以太阳能作为驱动力将水分解成氢气和氧气,是解决能源和环境危机的理想途径之一.α-Fe2O3是一种窄带隙(~2.1 eV)半导体,可以吸收约40%的太阳光,同时具有天然丰度高、成本低等优点,是目前备受关注的光阳极材料.然而,由于α-Fe2O3空穴扩散距离短和表面产氧动力学慢等缺点,导致α-Fe2O3的光电分解水效率仍然较低.针对上述问题,目前主要通过掺杂、构建异质结和负载助催化剂等手段来改善其性能.其中,负载助催化剂可以有效降低水氧化活化能和促进表面电荷分离,是改善光阳极性能的有效手段.本文采用离子吸附和螯合剂调控水解两步法,将Ni(OH)2量子点(Ni(OH)2 QDs)原位生长于α-Fe2O3表面,成功构建了Ni(OH)2 QDs/α-Fe2O3复合光阳极.透射电子显微镜结果表明,Ni(OH)2以直径为3–5 nm的量子点附着于α-Fe2O3纳米棒表面,并形成独特且牢固的异质结结构.光电水氧化性能表明,所制备的Ni(OH)2 QDs/α-Fe2O3光电阳极表现出良好的光电性能,其光电流达到了1.93 mA·cm?2(1.23 V vs.RHE),是单纯α-Fe2O3的3.5倍,且Ni(OH)2 QDs助催化剂使α-Fe2O3的起始电位降低了~100 mV.2 h稳定性测试结果表明,Ni(OH)2 QDs助催化剂在提升α-Fe2O3光电水氧化性能的同时,自身能够保持良好的稳定性,这在Ni(OH)2作为光电水氧化助催化剂的研究中较为少见.通过电化学活性面积、开路电压、电化学阻抗谱、注入效率和强度调制光电流谱等表征了Ni(OH)2 QDs对α-Fe2O3光阳极和电解液界面电荷传输的影响.结果表明,Ni(OH)2 QDs不仅能充分暴露水氧化活性位点,促进载流子在界面快速迁移,而且能有效钝化α-Fe2O3表面态,从而降低光生电子-空穴表面复合几率.本文可为多功能和高效量子点助催化剂/半导体光阳极的构建及在光电分解水制氢方面的应用提供一定借鉴. 相似文献
994.
本文报道以缺电子烯烃、胺类和二硫化碳为原料,以PEG-400为溶剂,在固体碱KF/nano-γ-Al_2O_3催化下,经微波辅助的Michael加成反应高效地合成二硫代氨基甲酸酯类化合物,收率为76.5%~91.6%。对催化剂、溶剂、微波功率、反应时间等影响因素进行了考察,确定了优化的反应条件。该方法具有反应时间短、收率高和环境友好等特点。另外,本文还报道了苯甲醛、酮类、胺类与二硫化碳四组分在PEG-400溶液中,在固体碱KF/nano-γ-Al_2O_3催化下,经微波辐射"一锅法"合成二硫代氨基甲酸酯类化合物的反应,收率为73.4%~82.8%。 相似文献
995.
Ding Su Ying Jiajin Chen Fei Fu Li Lv Yanfei Zhao Shichao Ji Guoqiang 《Journal of nanoparticle research》2021,23(4):1-9
Journal of Nanoparticle Research - In this work, a process of thermal decomposition of metal carbonyls in oxygen-enriched supercritical carbon dioxide was studied. Manganese, iron, cobalt, and... 相似文献
996.
钼团簇因具有独特的结构、电子和物理化学性质,被期待在未来的纳米科技中扮演重要角色,但是它们的基态结构至今还存在争议. 本研究采用粒子群优化(CALYPSO)方法对Mon (n=2∽18)团簇的晶体结构进行全局域能量最小化搜索,并结合第一性原理方法进一步优化. 计算表明:当4s和4p半核态不作为价态时,Mon (n=2∽18)团簇有明显的二聚体趋势,原子数为偶数的团簇往往是“幻数”团簇,具有较高的稳定性;但是,将4s和4p电子作为价电子后,平均杂化指数Hsp、Hsd和Hpd显著降低,二聚体趋势急剧减弱. 本文报道了Mon(n=11,14,15)团簇的新基态结构,证明了半核态对于Mon团簇是十分重要的. 相似文献
997.
The health condition of the rolling bearing seriously affects the operation of the whole mechanical system. When the rolling bearing parts fail, the time series collected in the field generally shows strong nonlinearity and non-stationarity. To obtain the faulty characteristics of mechanical equipment accurately, a rolling bearing fault detection technique based on k-optimized adaptive local iterative filtering (ALIF), improved multiscale permutation entropy (improved MPE), and BP neural network was proposed. In the ALIF algorithm, a k-optimized ALIF method based on permutation entropy (PE) is presented to select the number of ALIF decomposition layers adaptively. The completely average coarse-graining method was proposed to excavate more hidden information. The performance analysis of the simulation signal shows that the improved MPE can more accurately dig out the depth information of the time series, and the entropy value obtained is more consistent and stable. In the research application, rolling bearing time series are decomposed by k-optimized ALIF to obtain a certain number of intrinsic mode functions (IMFs). Then the improved MPE value of effective IMF is calculated and input into backpropagation (BP) neural network as the feature vector for automatic fault identification. The comparative analysis of simulation signals shows that this method can extract fault information effectively. At the same time, the experimental part shows that this scheme not only effectively extracts the fault features, but also realizes the classification and identification of different fault modes and faults of different degrees, which has a certain application prospect in the research and application direction of rolling bearing fault identification. 相似文献
998.
S. W. Zhang H. X. Lv F. P. Zhu M. Y. Zhang K. Yao 《Journal of Dispersion Science and Technology》2017,38(3):451-456
Polystyrene (PS)-encapsulated silica nanoparticles were successfully synthesized by conventional emulsion polymerization for solving the aggregation matter of nanoscaled silica. The grafting coupling agents and PS on the silica surface were detected by Fourier Transform Infrared (FTIR) spectroscopy. The influence of silica and monomer to water ratios and initiator concentration on particle size distribution of the nanocomposite latex was investigated. The particle size distribution firstly narrowed and then broadened with the increase of silica and monomer to water ratios and initiator concentration. The narrow distribution could be controlled in an appropriate silica and monomer to water ratio and an initiator concentration of 1/15 and 2 wt%, respectively. From the evaluation of transmission electron microscopy (TEM) micrographs and dynamic light scattering (DLS) measurement, it was proved that the nanocomposite latex did not have all sphere-like shape, but contained tiny amounts of irregular bodies. The formation mechanism of PS-encapsulated silica nanoparticles was also discussed. 相似文献
999.
本文采用"一锅法"将氧化石墨烯(GO)、炭黑(C)和钯离子用NaBH4共还原,制备了石墨烯-炭黑二元载体(Gr-C)负载的钯催化剂(20%Pd/Gr-C),用于催化甲酸的电氧化反应.电化学测试结果表明,前驱体GO和C的质量比为3:7的Pd/Gr0.3C0.7催化剂催化活性最好,它的峰电流密度(102.14 mA mgPd-1)约为Pd/C催化剂(34.40 mA mgPd-1)的3倍,为钯/石墨烯催化剂(Pd/Gr,38.50 mA mgPd-1)的2.6倍.甲酸在Pd/Gr0.3C0.7催化剂电极直接氧化时的峰电位比Pd/C催化剂的峰电位负移约120 mV,比Pd/Gr催化剂的峰电位负移约70 mV.采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、拉曼光谱、电感耦合等离子发射光谱(ICP-AES)等手段对催化剂进行了表征.从SEM图像可以观察到,球形的炭黑团簇聚集在具有褶皱的石墨烯面上,形成了炭黑团簇/石墨烯三维立体结构,有效地抑制了相邻石墨烯层在范德华力作用下的吸引聚集和堆叠造成的石墨烯表面积减小,减小了单层石墨烯叠合成为多层石墨所造成的导电性损失,避免了相邻石墨烯片叠合形成封闭空间,有助于反应物和产物分子的运动.载体的三维结构使反应物分子更容易到达钯纳米粒子,有利于催化性能的提高.XPS结果也证实了二元Gr-C载体对Pd催化的促进作用.Pd/Gr0.3C0.7催化剂的Pd 3d5/2峰发生了右移,表明Pd 3d电子结合能正移,Pd 3d电子云密度降低.具有较低的3d电子云密度的Pd不易与甲酸氧化过程中吸附的中间体(COOH)ads结合,钯催化剂上(COOH)ads表面覆盖率降低,从而使甲酸更容易直接脱氢氧化生成CO2,有利于甲酸通过直接途径进行电化学氧化.与Pd/C,Pd/Gr相比,Pd/Gr0.3C0.7催化剂对甲酸电氧化有最好的催化活性.Pd/Gr0.3C0.7催化剂优异的催化活性可归因于其内在的三维纳米结构:炭黑团簇有效地抑制了石墨烯纳米片的聚集,保持了其大的比表面积和高导电性,促进了反应物和产物分子的运动.此外,Pd纳米粒子与二元载体之间的强相互作用降低了Pd的3d电子云密度,使甲酸氧化主要经直接途径进行.本文证实了钯金属和石墨烯-炭黑二元载体之间的强相互作用,提供了简单和高性价比的方法以提高钯基催化剂的活性,有利于工业化的应用. 相似文献
1000.
The gel-spun ultra-high molecular weight polyethylene(UHMWPE) fibers were prepared at the industrial production line with different gel solution concentrations of 15 wt%, 18 wt% and 24 wt%. The difference in ultimate structure and mechanical properties of UHMWPE fibers for different gel solution concentrations were analyzed by tensile testing, differential scanning calorimetry(DSC), wide angle X-ray diffraction(WAXD) and small angle X-ray scattering(SAXS). With the increase of gel solution concentration, the ultimate mechanical properties of UHMWPE fibers were decreased and the crystallization and orientation of UHMWPE fibers became inferior. Besides, both the average shish length(〈L _(shish)〉) and shish misorientation(B_φ) of UHMWPE fibers were decreased with the increase of gel solution concentration. In addition, the appropriate increase of spinning temperature led to the further optimization of the ultimate structure and mechanical properties of UHMWPE fibers. 相似文献