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91.
92.
Optimization of preparation of thermally stable cellulose nanofibrils via heat‐induced conversion of ionic bonds to amide bonds
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Nathalie Lavoine Julien Bras Tsuguyuki Saito Akira Isogai 《Journal of polymer science. Part A, Polymer chemistry》2017,55(10):1750-1756
Improving the thermal stability of nanocelluloses is important for practical applications such as melt compounded nanocellulose‐reinforced polymer composites and flexible substrates for nanocellulose‐containing electronic devices. Here, we report optimum conditions for a straightforward surface modification strategy for improving the thermal stability of 2,2,6,6‐tetramethypiperidine‐1‐oxyl (TEMPO)‐oxidized cellulose nanofibrils (TOCNs); the heat‐induced conversion of TOCN alkyl ammonium carboxylates to amides. Different amine‐terminated compounds (R‐NH2) were grafted onto the surface of TOCNs under aqueous conditions. The influences of R‐NH2 molecular weight, R‐NH2/TOCN‐COOH molar ratio, and thermal stability of R‐NH2 on the properties of the grafted TOCN films were investigated through infrared spectroscopy and thermogravimetric analysis. For maximum thermal improvement of up to 90 °C, complete ionic bonding of TOCN carboxy groups with R‐NH2 was required, as well as proper selection of the R‐NH2 compound. A controlled heating process was also needed to achieve effective ionic‐to‐amide bond conversion. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1750–1756 相似文献
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Young Mi Park 《Experimental & molecular medicine》2014,46(6):e99
CD36 is a membrane glycoprotein that is present on various types of cells, including monocytes, macrophages, microvascular endothelial cells, adipocytes and platelets. Macrophage CD36 participates in atherosclerotic arterial lesion formation through its interaction with oxidized low-density lipoprotein (oxLDL), which triggers signaling cascades for inflammatory responses. CD36 functions in oxLDL uptake and foam cell formation, which is the initial critical stage of atherosclerosis. In addition, oxLDL via CD36 inhibits macrophage migration, which may be a macrophage-trapping mechanism in atherosclerotic lesions. The role of CD36 was examined in in vitro studies and in vivo experiments, which investigated various functions of CD36 in atherosclerosis and revealed that CD36 deficiency reduces atherosclerotic lesion formation. Platelet CD36 also promotes atherosclerotic inflammatory processes and is involved in thrombus formation after atherosclerotic plaque rupture. Because CD36 is an essential component of atherosclerosis, defining the function of CD36 and its corresponding signaling pathway may lead to a new treatment strategy for atherosclerosis. 相似文献
95.
以海藻酸钠(SA)为原料、高碘酸钠(SP)为氧化剂,通过调整SA与SP物质的量之比以及氧化时间,制备了不同氧化度的氧化海藻酸钠(OSA);以OSA为交联剂,制备了海藻酸钠/明胶(半)互穿网络膜(SA/Ge(semi)IPN)。通过红外光谱研究了(半)互穿网络膜的结构,推测了其交联机理;通过力学性能、交联度等测试方法研究了OSA的氧化度对(半)互穿网络膜力学性能的影响。结果表明:通过控制SA与SP物质的量之比可以制备特定氧化度的OSA;(半)互穿网络膜的力学性能随着OSA氧化度的增加呈现先增加后降低的趋势,而交联度随着OSA氧化度的增加而增加。 相似文献
96.
采用一步合成法制备磁性氧化石墨烯材料(GO-Fe_3O_4),将其用作磁性固相吸附剂对环境水样中的6种三嗪类除草剂进行萃取和富集,并与高效液相色谱-串联质谱法相结合进行测定。以扫描电镜和傅立叶红外光谱对合成材料进行了表征,并考察了GO-Fe_3O_4用量、萃取时间、水样的pH值及离子强度和解吸条件等因素对萃取效率的影响。6种三嗪类除草剂的检出限为0.1~1.0 ng/L,富集倍数可达616~902倍。将方法应用于苏州地区太湖水、运河水和护城河水等实际水样的分析,加标回收率为85.4%~117.6%,相对标准偏差为1.2%~10.0%。该方法操作简单快速,富集倍数较高,检出限低,可用于水样中痕量三嗪类除草剂残留的检测。 相似文献
97.
采用搅拌球磨机对木薯淀粉进行机械活化,以活化60min的木薯淀粉为原料,CuSO4为催化剂,H2O2为氧化剂干法制备氧化淀粉。利用红外光谱、扫描电子显微镜、X-射线衍射等手段对产物的结构进行表征分析,并与原淀粉的氧化产物进行比较。结果表明,机械活化对木薯淀粉的氧化反应有显著的影响。原木薯淀粉的氧化反应主要发生在淀粉颗粒的表面及无定形区,部分发生在结晶区,产物是无定形及结晶状态的结构;活化淀粉的氧化反应在淀粉团粒表面及内部均匀进行,产物是无定形的聚集状态结构。并就机械活化对淀粉氧化的强化机理进行了探讨。 相似文献
98.
Hong J Miao R Zhao C Jiang J Tang H Guo Z Zhu L 《Journal of mass spectrometry : JMS》2006,41(8):1061-1072
Interaction of cis-[Pt(en)(H2O)2]2+ and [CuL(H2O)]2+, where L is 2-[bis(2-aminoethyl)amino]ethanol, with oxidized insulin B chain in molar ratio of 1 : 1, 1 : 2 and 1 : 3 at pH 2.5 and 40 degrees C has been investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The results show that the binding sites of the two complexes with oxidized insulin B chain are terminal NH2, imidazole groups of His5 and His10. The hydrolytic cleavage studies show that the [CuL(H2O)]2+, upon a pendant hydroxyl group of the ligand, selectively cleaves the peptide bonds at Gly8-Ser9, Asn3-Gln4 and Phe1-Val2, and the cis-[Pt(en)(H2O)2]2+ only cleaves the peptide bond at His10-Leu11. This is the first report of cis-[Pt(en)(H2O)2]2+-promoted cleavage of His-X peptide bond. 相似文献
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100.
Rákosi Éva Dávid 《Mikrochimica acta》1989,97(5-6):387-391
Determination of phosphate was performed with lanthanum nitrate in an aqueous medium in the presence of a haematoxylin indicator. Following processing of the organic phosphorus compound in a Schöniger flask the mixture was acidified and boiled off and then the pH was adjusted to 6.1–6.3 with hexamethylene tetramine. The hot solution was titrated with lanthanum nitrate. The orange colour of haematoxylin changed to violet-blue at the point of equivalence, while precipitation of lanthanum phosphate was observed. 相似文献