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Theoretical and Mathematical Physics - We apply the Riemann–Hilbert method to the generalized mixed nonlinear Schrödinger equation and obtain a new formula for an explicit $$N$$ -soliton... 相似文献
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协效剂对膨胀阻燃聚丙烯基木塑复合材料的阻燃增效研究 总被引:1,自引:1,他引:0
赋予木塑复合材料(WPC)的阻燃性能成为近年来该领域国内外的研究热点之一。本文通过两轮正交试验,研究8种常见的协效剂对膨胀型阻燃剂(IFRs,m(聚磷酸铵,APP)∶m(季戊四醇,PER)=2∶1)的阻燃增效作用,筛选出具有显著协效作用的协效剂组MgO/EG(可膨胀石墨)/SiO_2,其组成为m(MgO)∶m(EG)∶m(SiO_2)=1∶5∶5,其与IFRs的最佳配比为m(IFRs)∶m(MgO/EG/SiO_2)=1∶0.18,得到性能良好的阻燃型聚丙烯基木塑复合材料。通过热重分析(TGA)和锥形量热分析(CONE)评价IFRs及协效剂组对聚丙烯(PP)基木塑复合材料(WPC)热稳定性能和阻燃性能的影响。结果表明,IFRs及MgO/EG/SiO_2的加入可以有效提高WPC的热稳定性,WPC/IFRs/MgO/EG/SiO_2600℃的残炭率达到22.42%。WPC/IFRs的热释放速率峰(PHRR)、总热释放量(THR)和总烟释放量(TSP)相比于WPC分别降低了21.9%、8.7%和22%。MgO/EG/SiO_2的加入可以进一步提高IFRs的阻燃效率,WPC/IFRs/MgO/EG/SiO_2的PHRR和THR相比于WPC分别降低了33.0%和13.8%。 相似文献
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1991年刘振宏和李明楚在南京大学召开的首届哈密顿图研讨会的综述文章中说"要给出一个一般图具有哈密顿圈的充分条件是一件非常不容易的事"。因哈密顿图是含哈密顿圈的图类,如此哈密顿图主要有六个方向:哈密顿圈、哈密顿连通、泛圈图、点泛圈图、泛连通图、最短路径泛圈图。本文中,我们就给出一般图的这些领域新进展的小综述。 相似文献
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用甲苯-2,4-二异氰酸酯(TDI)和硬脂酸(SA)复合改性木粉,在双螺杆挤出机中制备了聚丙烯(PP)基的木塑复合材料(WPC),研究了SA/TDI摩尔比对木粉表面性能、复合材料力学性能和加工性能的影响。 结果表明,随着SA/TDI摩尔比的增大,改性木粉的表面张力逐渐减小,与PP的界面张力先减小后增大;与未改性的WPC相比,SA/TDI复合改性剂对WPC的拉伸强度、弯曲强度、缺口冲击强度影响不明显,但对无缺口冲击强度提升较大;当SA/TDI摩尔比为1.07时,复合材料的无缺口冲击强度和熔体质量流动速率分别达到9.74 kJ/m2和13.12 g/10 min,分别比未改性WPC提高了77%和22%。 相似文献
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用马来酸酐(MAH)在碳酸钙(CaCO3)表面引入双键,通过原位固相接枝法将聚丙烯蜡(PPW)化学键合在CaCO3表面,制得3种接枝率的CaCO3-MAH-PPW。 将这3种改性CaCO3填充聚丙烯(PP)制备复合材料,研究了PP/CaCO3界面作用对复合材料强度的影响。 结果表明,CaCO3表面经PPW接枝改性后在PP中的分散性提高,与PP相容性变好;随着改性CaCO3表面PPW接枝率的提高,CaCO3与PP之间界面作用逐渐增强。 当PPW接枝率为4.48 mg PPW/g CaCO3时,CaCO3与PP之间的界面作用最强,复合材料拉伸强度下降最小,杨氏模量提升最大,当m(PP)∶m(CaCO3)=100∶50时,杨氏模量达0.86 GPa,是纯PP的1.63倍;而PPW化学接枝率为2.49 mg PPW/g CaCO3时,CaCO3与PP之间的界面作用适中,复合材料缺口冲击强度提升最大,且当m(PP)∶m(CaCO3)=100∶10时,缺口冲击强度达3.91 kJ/m2,是纯PP的1.35倍。 相似文献
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We reported here an efficient regioselective protection strategy for xylose with two-step successive protections on 4- and 2-OH. This method enables the expeditious preparation of various xylose building blocks (3a–c, 5, 6). The rapid selective 2,4-protection especially facilitates the synthesis of 3-substituted xyloside structures. By this approach, typical arabino-α-1,3-xyloside disaccharide and trisaccharide, as fragment structure units from arabinoxylans, have been successfully synthesized. 相似文献
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Staphylococcal food poisoning is one of the most common foodborne diseases worldwide; it results from the ingestion of staphylococcal enterotoxins (SEs) in food, mainly Staphylococcus aureus. This study investigated the statistical relationships among morphological enumerations of food-derived S. aureus and production of SEs using different methodologies. Food samples naturally contaminated with coagulase-positive S. aureus were submitted for enumeration on Baird-Parker (BP) agar, Rabbit Plasma Fibrinogen agar (RPFA), and Petrifilm Staph Express count system (STX), and the morphologically typical colonies were isolated for VIDAS and real-time (RT) PCR tests. RPFA and STX displayed better performance for the enumeration of SE-positive S. aureus when compared with BP, including higher frequencies of SE-positive isolates and better correlation indices between typical and SE-positive counts. Among all the evaluated culture media, no significant difference (P > 0.05) was shown on the frequencies of typical colonies that carried 11 individual se genes. In addition, results for SE identification between VIDAS and RT-PCR assay were unparalleled. These data will be valuable for the selection of methods for inspection of food-derived S. aureus. 相似文献
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Two silylated BODIPY derivatives were synthesized, characterized and used for the fabrication of the dye-encapsulated silica nanoparticles. The fluorophores were covalently incorporated into the silica matrix to minimize any fluorophore leakage. The synthesized fluorophore-doped nanoparticles were stable in aqueous solution and monodisperse with diameters of 20-25 nm. By incorporating the two BODIPY dyes simultaneously at a controlled ratio, silica nanoparticles with switchable emitting wavelengths were achieved with a change in the excitation wavelength. Thus by using the dual-fluorophore-doped nanoparticles, two-color imaging was demonstrated with minimal background signal by employing an appropriate excitation light source and appropriate excitation/emission filter sets. Further, the surfaces of the dual-fluorophore-doped nanoparticles were functionalized with folic acid to allow for the recognition of HeLa cells which over-express the folate receptors. 相似文献
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Hongmin Zhang Xintong Hu Miao Qiao Yang Li Shijie Cao Liqin Ding Xinchi Feng Ning Kang Deqin Zhang Feng Qiu 《Journal of separation science》2019,42(16):2592-2601
A rapid and sensitive liquid chromatography with tandem mass spectrometry method was developed and validated for simultaneous determination of puerarin, daidzin, daidzein, 3′‐hydroxy puerarin, and genistein in rat plasma after oral administration of Puerariae lobatae radix extract. The method of protein precipitation with acetonitrile was used for sample preparation. Chromatographic separation was achieved on a C18 column with the mobile phases of acetonitrile/water containing 0.1% formic acid. The analytes were detected by mass spectrometer with an electrospray ionization source operating in the negative ion mode. The linearity, precision, accuracy, dilution reliability, recovery, matrix effects, and stability of the method were within acceptable ranges. The developed method was successfully used to compare the pharmacokinetic characteristics of five analytes in normal and type 2 diabetics rats after oral administration of Puerariae lobatae radix extract. Several pharmacokinetic alterations were observed and this might be caused by the pathological state of type 2 diabetes. 相似文献