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71.
Encapsulating proteins in polymeric microspheres is a useful mode of drug delivery, but the proteins are subjected to damage in the process of ultrasound emulsion microencapsulation. The objective of this study was to investigate the effects of ultrasound power and duration on the function and structure of trypsin, and the reason of protein denaturation when it was irradiated by 20 kHz ultrasound. The relatively stable enzyme, trypsin, was dissolved in aqueous solution in the presence and absence of additives to study the stability of trypsin during the ultrasound irradiation. The damage of the molecular structure of trypsin was detected via combined high performance liquid chromatogram and electrospray ionization mass spectrometry (HPLC–ESI-MS). The results showed that the activity of trypsin decreased with increasing ultrasound power from 100 to 500 W or extending the irradiation time from 1 to 20 min. This effect could be enhanced via aerating the solution for a duration 10 min at 300 W. Fragments of trypsin were detected in the treatment (300 W, 10 min) by HPLC–ESI-MS. The additives, Tween 80 and mannitol, could protect trypsin against the inactivation caused by ultrasound. The reason of inactivation was partly from the alteration of the molecular conformation and partly from the modification or damage of trypsin's molecular structure. 相似文献
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《中国化学快报》2020,31(9):2375-2394
Furazan and furoxan represent fascinating explosophoric units with intriguing structures and unique properties. Compared with other nitrogen-rich heterocycles, most poly furazan and furoxan-based heterocycles demonstrate superior energetic performances due to the higher enthalpy of formation and density levels. A large variety of advanced energetic materials have been achieved based on the combination of furazan and furoxan moieties with different kinds of linkers and this review provides an overview of the development of energetic poly furazan and furoxan structures during the past decades, with their physical properties and detonation characteristics summarized and compared with traditional energetic materials. Various synthetic strategies towards these compact energetic structures are highlighted by covering the most important cyclization methods for construction of the hetercyclic scaffolds and the following modifications such as nitrations and oxidations. Given the synthetic availabilities and outstanding properties, energetic materials based on poly furazan and furoxan structures are undoubtedly listed as a promising candidate for the development of new-generation explosives, propellants and pyrotechnics. 相似文献
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Preparation of magnetic Fe3O4/P (GMA‐DVB)‐PEI/Pd highly efficient catalyst with core‐shell structure
Mingliang Ma Yuying Yang Yanyan Liu Wenting Li Guopeng Chen Yong Ma Ping Lyu Shunhe Li Yubao Wang Guanglei Wu 《应用有机金属化学》2019,33(5)
In this paper, a simple route for palladium (Pd) nanoparticles attached to the surface of hollow magnetic Fe3O4/P (GMA‐DVB)‐polyethyleneimine (PEI) microspheres was established. Due to the large amount of imidogen groups and tertiary amine groups presenting in the PEI, Pd2+ ions could be anchored to the support by complexation with a polyfunctional organic ligand. Thereafter, a magnetic Pd catalyst having a high loading amount and good dispersibility was obtained by reducing Pd2+ ions. Afterwards, the prepared catalyst was characterized by TEM, SEM, FTIR, XRD, TGA, VSM, and UV–vis in detail. Ultimately, their catalytic activity was evaluated using the reduction of 4‐nitrophenol (4‐NP). Research showed that the Fe3O4/P (GMA‐DVB)‐PEI/Pd catalyst possessed high catalytic performances for the reduction of 4‐NP with a conversion rate of 98.43% within 540 s. Furthermore, the catalyst could be easily recovered and reused at least for nine successive cycles. 相似文献
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With the rapid development of ytterbium-doped fiber lasers, some obtrusive limitations on power scaling appeared. In order to avoid these problems, a scheme called tandem pumping is introduced into the fiber laser field. In this paper, the optical properties of an ytterbium-doped tandem-pumped fiber oscillator are presented. According to the oscillator profile, the proper gain fiber type and pump wavelength range are picked out, under the comprehensive consideration of laser conversion efficiency and beam quality. In addition, the photodarkening performances of tandem pumping lasers and conventional ones are compared based on practical application, with all possible impact parameters taken into account. Moreover, an all-fibered tandem-pumped oscillator centered at 1079.5 nm is built, in the way of clad pumping by a 1030-nm fiber laser. The laser power of the oscillator reaches 7 W, with an opto-optic efficiency of 82.4%. 相似文献
78.
选取2003-2015年我国沪深A股上市公司中有境外机构投资者(QFII)持股的公司作为研究样本,将QFII持股周期划分为短期、中期和长期三类,通过理论分析和实证分析研究QFII不同持股周期对上市公司治理绩效的影响,研究结果表明,QFII短期持股时,奉行财务投资理念,通过买卖价差获取投资收益,不会对公司治理绩效产生影响;QFII中期持股时,会对公司治理绩效产生影响,但影响作用较微弱;QFII长期持股时,主要奉行价值投资理念,通过积极参与公司治理影响公司治理绩效,获得高额投资收益。本文的研究结论对我国境内机构投资者和上市公司具有一定的借鉴作用,同时可以为我国引入QFII提供政策建议。 相似文献
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在Al-In-Zn-Sn合金的基础上,掺入Ce形成合金样品,将样品进行重熔与磁场凝固处理制成研究电极,通过SEM对其表面形态进行了分析,并在4 mo.lL-1的KOH溶液中进行阳极极化曲线、交流阻抗、恒流放电等电化学性能测试。结果表明:磁场凝固处理能够提高Al-In-Zn-Sn-Ce合金的腐蚀电位,减小阳极材料的阻抗,改善阳极的放电性能。 相似文献