排序方式: 共有250条查询结果,搜索用时 15 毫秒
21.
Huanhuan Cui Yingxing Wang Shenghui Li Changhu Xue 《Journal of carbohydrate chemistry》2013,32(5-6):398-411
AbstractA galactoglucan (HCPA) was extracted from C. mollissima Blume fruits using hot water, which was composed of glucose and galactose, with a molecular weight of 5.5?kDa. Methylation and 1?D, 2?D NMR spectroscopy analysis showed that HCPA contained [→4)-α-D-Glcp(1→], [→4,6)-α-D-Glcp(1→], [→4)-β-D-Galp(1→] and [α-D-Glcp(1→] motifs in a molar ratio of approximately 6.11:1.08:1.00:1.03. HCPA showed a spherical-like structure as detected by scanning electron microscope (SEM). HCPA biological activity was investigated in vitro. The results showed that HCPA inhibited the proliferation of HeLa, MCF-7 and MGC-803 cells, induced HeLa cells apoptosis and arrested cell cycle in G2/M phase of HeLa cells. HCPA also enhanced the viability and phagocytic ability of RAW 264.7 cells and stimulated the production of NO, TNF-α and IL-6. The results demonstrated that HCPA had a potent antitumor and immunomodulating effects in vitro, suggesting its potential use as functional food and drug products. 相似文献
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Leilei Wang Wei Wei Daoshan Yang Huanhuan Cui Huilan Yue Hua Wang 《Tetrahedron letters》2017,58(51):4799-4802
A facile and efficient one-pot method has been developed for the construction of alkynyl sulfones via direct cross-coupling reaction of aryl alkynyliodines and arylsulfinic acids. The present transformation could be accomplished under catalyst- and additive-free conditions, providing a series of alkynyl sulfones in moderate to good yields with favorable functional group tolerance. 相似文献
24.
Donglei Sun Jiantao Fu Yinglin Lu Lijun Chen Hengliang Gong Huanhuan Zhao 《International journal of environmental analytical chemistry》2017,97(8):783-795
The neonicotinoid imidacloprid is a very important insecticide in maize cultivation in China. A laboratory experiment was conducted to investigate its absorption, transportation and distribution in maize plants. Plants were exposed to an aqueous solution of imidacloprid at five concentrations (10, 20, 50, 100 and 200 μg/mL). The residues of imidacloprid in different plant parts were determined by using a quick and effective method of high-performance liquid chromatography. Results showed that the average recoveries ranged from 85.16% to 102.23%, with relative standard deviations of 1.82–4.40% at three different spiking levels in each different matrix. The half-lives of imidacloprid in hydroponic maize water were from 5.33 to 11.55 days. The concentrations in roots, stems and leaves were from 5.61 to 7.48, 1.03 to 4.03 and 0 to 30.57 μg/mL after 6 h–7 days exposed in 10 μg/mL imidacloprid aqueous solutions, respectively. Our study showed that imidacloprid was strongly absorbed by roots and mainly accumulated in leaves. Quantity ratio and bioconcentration factors (BCFs) were also used to estimate the distribution and accumulation in maize. The values of quantity ratios were the highest in the leaves while lowest in the root after 7 days treatments, with the ranking of leaves > stem > root. The BCFs were 0.63–1.66, 0.52–0.92 and 3.20–6.78 in root, stem and leaves, respectively. These results demonstrated that the exposed time and imidacloprid application concentrations were also the main factors influencing the absorption. This study enhances our understandings of the uptake and distribution of imidacloprid in maize plants. 相似文献
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A new photochromic diarylethene (1a) has been prepared. Both its photochromic behavior and nonlinear optical properties are
investigated. 1a shows excellent ring-opening (λmax = 386 nm) and ring-closing (λmax = 652 nm) photoisomerization with UV-Vis light irradiation. With 800 nm femtosecond pulsed laser irradiation, 1a shows two-photon-induced
photoisomerization, and a two-photon absorption cross-section (σ = 423×1050 cm4·s per photon) is obtained by using two-photon induced fluorescence method. The applications of two-photon absorption of 1a
to holographic recording has been also investigated. A two-photon induced micro-pattern is recorded on the diarylethene 1a-PMMA
film with an femtosecond laser of 800 nm, 100 fs, 1 kHz, 50 mW. 相似文献
26.
Huanhuan KouXin Zhang Yongling DuWeichun Ye Shaoxiong LinChunming Wang 《Applied Surface Science》2011,257(10):4643-4649
Well-aligned ZnO nanoflowers and nanosheets were synthesized on porous Si (PS) at different applied potentials by electrodeposition approach. The deposits were grown using the optimized program and were characterized by means of cyclic voltammetry (CV), amperometry I-t (I-t), open-circuit potentiometry. X-ray diffraction (XRD) analysis proved a strong preferential orientation (1 0 0) on PS. Scanning electronic microscopy (SEM) observation showed the deposits consist of nanoflowers with uniform grain size of about 100 nm in diameter and nanosheets, which may have potential applications in nanodevices and nanotechnologies. Thus, ZnO grown on PS can be used as photoelectric materials due to its larger photoelectric effect compared to Si wafer according to open-circuit potential (OCP) study. Optical band gap measurements were made on samples using UV-visible spectrophotometer thus giving a band gap of 3.35 eV. 相似文献
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Guoliang Jiang Huanhuan Cai Zhihao Shen Xinghe Fan Qifeng Zhou 《Journal of polymer science. Part A, Polymer chemistry》2013,51(3):557-564
A series of mesogen‐jacketed liquid crystalline polymers, poly{2,2,3,3,4,4,4‐heptafluorobutyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PF3Cm, where m is the number of carbon atoms in the alkoxy groups, and m = 1, 4, 6, and 8), the side chain of which contains a biphenyl core with a fluorocarbon substituent at one end and an alkoxy unit of varying length on the other end, were designed and successfully synthesized via atom transfer radical polymerization. For comparison, poly{butyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PC4Cm), similar to PF3Cm but with a butyl group instead of the fluorocarbon substituent, was also prepared. Differential scanning calorimetric results reveal that the glass transition temperatures (Tgs) of the two series of polymers decrease as m increases and Tgs of the fluorocarbon‐substituted polymers are higher than those of the corresponding butyl‐substituted polymers. Wide‐angle X‐ray diffraction measurements show that the mesophase structures of these polymers are dependent on the number of the carbon atoms in the fluorocarbon substituent and the property of the other terminal substituent. Polymers with fluorocarbon substituents enter into columnar nematic phases when m ≥ 4, whereas the polymer PF3C1 exhibits no liquid crystallinity. For polymers with butyl substituents, columnar nematic phases form when the number of carbon atoms at both ends of the side chain is not equal at high temperatures and disappear after the polymers are cooled to ambient temperature. However, when the polymer has the same number of carbon atoms at both ends of the side chain, a hexagonal columnar phase develops, and this phase remains after the polymer is cooled. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
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Huanhuan Gao Xiaojun Huang Xiongwei Ma Xiaoyan Li Linyan Guo Helin Yang 《Frontiers of Physics》2023,18(4):42301
Pancharatnam−Berry (PB) phase metasurface, as a special class of gradient metasurfaces, has been paid much attention owing to the robust performance for phase control of circularly polarized waves. Herein, we present an element-based polarizer for the first step, which enables the incident electromagnetic waves into the cross-polarized waves with the relative bandwidth of 71%, and the polarization conversion ratio exceeds 90% at 6.9−14.5 GHz. Then an eight-elements coding polarizer based on the PB phase is presented for the applications on beam control and radar cross section reduction. The simulated values indicate that the reduction of radar cross section is more than 10 dB at 6−16 GHz. Our work reveals the availability of manipulating the waves, beamforming in communication systems and electromagnetic stealth, and so on. 相似文献
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以氯化1-丁基-3-甲基咪唑鎓([Bmim]Cl)和二元羧酸为原料,由不同摩尔比混合制备了一类新型低共熔溶剂,采用红外光谱对[Bmim]Cl和二元羧酸之间的作用进行了分析。分别测定了其粘度、电导率、密度、折射率等物理性质,并研究了温度、二元羧酸结构和摩尔比对这些物理性质的影响。结果表明,新型低共熔溶剂的粘度随温度的升高而降低,电导率随温度的升高而增加。温度对两者的影响可以采用VTF方程进行精确地拟合。新型低共熔溶剂的密度随温度的升高而呈线性下降。对新型低共熔溶剂的过量摩尔体积进行计算的结果表明,过量摩尔体积均为正值,二元羧酸对过量摩尔体积的贡献远大于[BMIM]Cl,而结构特性的贡献多于物理作用。折射率和密度随二元羧酸碳数的变化趋势基本相似。 相似文献
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Let A and B be algebras, and let T be the dual extension algebra of A and B. We provide a different method to prove that T is Koszul if and only if both A and B are Koszul. Furthermore, we prove that an algebra is Koszul if and only if one of its iterated dual extension algebras is Koszul, if and only if all its iterated dual extension algebras are Koszul. Finally, we give a necessary and sufficient condition for a dual extension algebra to have the property that all linearly presented modules are Koszul modules, which provides an effective way to construct algebras with such a property. 相似文献