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排序方式: 共有870条查询结果,搜索用时 343 毫秒
61.
采用商品化SKE-1型环氧树脂对自制聚氨酯预聚体(NCOPU)进行封端,制备了缩水甘油胺型聚氨酯(GAPU),并用傅里叶-红外光谱(FT-IR)对其结构进行表征,用在线FT-IR监控间苯二甲胺固化GAPU过程,用差示量热扫描(DSC)研究其相分离,用扫描电镜(SEM)观察固化物的表面微观形貌,用热重(TG)分析固化物的热力学稳定性。探讨了聚丙二醇(PPG)分子量的大小、不同质量分数的SKE-1对NCOPU封端及不同种类的固化剂对GAPU固化物力学性能的影响。研究表明:在60℃时用间苯二甲胺固化GAPU,2h即可固化完全,固化物热稳定性能良好,其外推起始分解温度为248.3℃,5%的分解温度为282.6℃。GAPU固化物的力学性能随着GAPU的环氧值减小而减小,在室温以上力学性能下降,在-196℃力学性能增加,其环氧值为0.153,在-196℃的拉伸剪切强度最佳,为16.11MPa。 相似文献
62.
Qi Wang Hongjun Ni Annette Pietzsch Franz Hennies Yongping Bao Yimin Chao 《Journal of nanoparticle research》2011,13(1):405-413
Water-dispersible silicon nanoparticles (Si-NPs) are desirable for applications in biological techniques. A simplified method
to synthesize such particles is reported here. The resulting Si-NPs are water-dispersible and luminescent. Under the excitation
of UV light, the Si-NPs emit strong red light with a peak maximum at 606 nm and a quantum yield of 6%. They are highly stable,
and remain so over several weeks. Fourier Transform Infrared (FTIR) spectroscopy shows a visible Si–CH2 scissoring vibration mode. Furthermore, the surface chemical bondings were confirmed by X-ray photoelectron spectroscopy
(XPS). In the Si2p and C1s core levels, Si–C components are observed. The diameters of the synthesized Si-NPS as measured by atomic force microscope (AFM) are approximately
5 nm. Furthermore, the nanoparticles can be taken up by cultured cells. Fluorescence images of Si-NPs within MCF-7 human breast
cancer cells show they are distributed throughout the cell tissue. 相似文献
63.
对人类在线行为模式的探讨是近年来人类动力学研究的热点.基于维基百科数据,文章针对一类重要且普遍的在线行为--在线协同写作,进行时间统计特性分析和内容更新统计分析.实证显示在线协同写作时间间隔分布呈多尺度特征,1 min到30 min和30 min到24 h两个时间段上时间间隔分别服从指数为1.62和1.16的幂律分布,而大于24 h的时间间隔服从形如F(τ)∝τ-b-alog(τ)的累积分布.分析表明
关键词:
在线协同写作
人类动力学
多尺度特征
维基百科 相似文献
64.
Chao Song Jun Xu Quanbiao Wang Guowei Zha Kunji Chen 《Solid State Communications》2011,151(9):697-700
Phosphorus- and boron-doped hydrogenated amorphous silicon thin films were prepared by the plasma-enhanced chemical vapor deposition method. As-deposited samples were thermally annealed at various temperatures to get nanocrystalline Si with sizes around 10 nm. X-ray photoelectron spectroscopy measurements demonstrated the presence of boron and phosphorus in the doped films. It is found that the nanocrystallization occurs at around 600 °C for the B-doped films, while it is around 700-800 °C for the P-doped samples. For the P-doped samples, the dark conductivity decreases at first and then increases with the annealing temperature. While for the B-doped samples, the dark conductivity monotonously increases with increasing annealing temperature. As a result, the carrier transport properties of both P- and B-doped nanocrystalline Si films are dominated by the gradual activation of dopants in the films. The conductivity reaches 22.4 and 193 S cm−1 for P- and B-doped sample after 1000 °C annealing. 相似文献
65.
In this article, we discuss some properties of a supersymmetric invariant bilinear form on Lie supertriple systems. In particular, a supersymmetric invariant bilinear form on Lie supertriple systems can be extended to its standard imbedding Lie superalgebras. Furthermore, we generalize Garland's theory of universal central extensions for Lie supertriple systems following the classical one for Lie superalgebras. We solve the problems of lifting automorphisms and lifting derivations. 相似文献
66.
Xiaoyu Li He Liu Yongping Xu Fanxing Xu Linhui Wang Jiansong You Shuying Li Liji Jin 《Applied biochemistry and biotechnology》2012,168(6):1448-1458
Solobacterium moorei is a causative agent in diseases such as oral halitosis, bacteremia, and necrobacillosis-associated thrombophlebitis. The objective of this study was to determine the effectiveness of chicken egg yolk antibody (IgY) in controlling S. moorei. Intact S. moorei cells were used as an immunogen to immunize four White Leghorn laying hens. IgY, extracted from egg yolks obtained from these immunized hens, was purified using water dilution, two-step salt precipitation, and ultrafiltration. The purity of the IgY obtained was approximately 87.3?%. The antibody titer of the IgY was determined by enzyme-linked immunosorbent assay. The antibody titer peaked at 10,000 following the third immunization. In order to evaluate the inhibitory effects of the specific IgY, the growth of S. moorei in liquid media was measured every 12?h using a microplate reader at 600?nm. Biofilm formation of S. moorei was quantified by staining with crystal violet. The specific binding ability of IgY was further confirmed by the use of immunofluorescence and immunoelectron microscopy. Growth and biofilm formation of S. moorei were significantly (P?<?0.05) inhibited by 20 and 40?mg/ml specific IgY compared with the control. The specific IgY also decreased the bacterial level in the oral cavity of mice after infection with S. moorei. This study demonstrates that the growth and biofilm formation of S. moorei can be effectively inhibited by specific IgY. As a result, IgY technology may have application in the control of diseases caused by S. moorei. 相似文献
67.
The compatible carbon-silicon complex materials originated from precursor diglycerylsilane (DGS) and sugar-modified silane
N-(3-triethoxysilylpropyl)gluconamide (GLS) have gained substantial popularity by demonstrating admirable properties to stabilize
entrapped biomolecules. The microenvironment inside these materials, especially the distribution of sugar moieties inside
the matrix, which is likely the most critical factor determining compatibility of these materials, still remains unclear.
To deeply investigate the biocompatibility mechanism of these materials, we have adopted two different preparation routes
for these materials by introducing GLS into the starting DGS sol stage, but things are different after the DGS gel is formed.
A fluorescence probe rhodamine 6G is introduced herein in the DGS sol to monitor the distribution of GLS moieties, as well
as the evolution of the microenvironment inside resulting materials. All in all, the findings demonstrated that the timing
of GLS addition plays a critical role in controlling the evolution of the inner structure of materials, suggesting that this
factor provides a promising route to tune the properties of the resulting materials.
Supported by the National Natural Science Foundation of China (Grant No. 20876176), Scientific Research Foundation for the
Returned Overseas Chinese Scholars by the State Education Ministry, Key Project of Chinese Ministry of Education (Grant No.
109100), Doctoral Project of Shandong Province (Grant No. 2008BS09013), Research Foundation of Key Laboratory of Carbon Materials,
Institute of Coal Chemistry, CAS (Grant No. KFJJ0506), and Natural Science Foundation of Shandong Province (Grant No. Q2007B02) 相似文献
68.
Xiang‐Ping Zha Yan‐Yan Zhao Yong‐Fei Zheng 《Rapid communications in mass spectrometry : RCM》2010,24(15):2217-2226
An online method using continuous flow isotope ratio mass spectrometry (CF‐IRMS) interfaced with a Gasbench II device was established to analyze carbon and oxygen isotopic compositions and to estimate the content of minor amounts of carbonate in silicate rocks. The mixtures of standard materials and high‐purity quartz are firstly used to calibrate different quantities of carbonate in silicates. The results suggest that the accuracy and precision of the online analysis are both better than those obtained using an offline method. There is a positive correlation between the carbonate weight and the Mass44 ion beam intensity (or peak area). When the weight of carbonate in the mixtures is greater than 70 µg (equal to ~1800 mV Mass44 ion beam intensity), the δ13C and δ18O values of samples usually have accuracy and precision of ±0.1‰ and ±0.2‰ (1σ), respectively. If the weight is less than 70 µg, some limitations (e.g., not perfectly linear) are encountered that significantly reduce the accuracy and precision. The measured δ18O values are systematically lower than the true values by ?0.3 to ?0.7‰; the lower the carbonate content, the lower the measured δ18O value. For samples with lower carbonate content, the required phosphoric acid doses are higher and more oxygen isotope exchanges with the water in the phosphoric acid. To guarantee accurate results with high precision, multiple analyses of in‐house standards and an artificial MERCK sample with δ13C values from ?35.58 to 1.61‰ and δ18O from 6.04 to 18.96‰ were analyzed simultaneously with the unknown sample. This enables correction of the measured raw data for the natural sample based on multiple‐point normalization. The results indicate that the method can be successfully applied to a range of natural rocks. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
69.
70.
报告了一种新的长焦距光学系统杂光系数测量装置,该装置除具有避免了制作大直径积分球的优点外,还能精确测量轴外杂光系数,分析各部分杂光源对杂光系数的影响. 相似文献