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81.
A new kinetic spectrophotometric method for the determination of hydrazine is described. The method is based on the inhibitory
effect of hydrazine on the reaction of neutral red with nitrite in acidic media and 28 °C. A product from the reaction of
neutral red with nitrite was used to monitor the reaction spectrophotometrically at 352 nm. Hydrazine can be determined in
the range 4.7×10−6∼3.1×10−5mol/L with a detection limit of 3.1×10−6mol/L. The method was applied to the determination of hydrazine in water samples.
Received July 23, 1999. Revision January 10, 2000. 相似文献
82.
The exploration of a dual-functional sensor is the key to effectively detect the Cr(Ⅵ)and Fe(Ⅲ)cations in water,which is important to human health and environme... 相似文献
83.
We count the number of cyclic strings over an alphabet that avoid a single pattern under two different assumptions. In the first case, we assume that the symbols of the alphabet are on numbered positions on a circle, while in the second case we assume that the symbols can be freely rotated on the circle (i.e., we deal with necklaces). In each case, we provide a generating function, and we explain how these two cases are related. For the situation of avoiding more than one pattern, we formulate a general conjecture for the first case, and a conditional result for the second case. We also explain the differences between our theory and the theory of Edlin and Zeilberger (2000) by emphasizing how we modified the definition of the enumeration of cyclic strings that avoid one or more patterns when their lengths are less than the length of the longest pattern. 相似文献
84.
高凌云 《数学年刊A辑(中文版)》2018,(4):367-376
利用Nevanlinna值分布理论,研究了两类复合函数-差分方程超越解的性质,超越解的特征函数,非积分计数函数及其存在性,并相应地给出估计. 相似文献
85.
Lingyun Dong Xusheng Ge Pengfei Zhang Qian Li Sufang Sun Shigang Shen 《无机化学与普通化学杂志》2019,645(14):944-948
By the application of cation substitution, a new mixed‐alkali metal diphosphate, K2Li2P2O7, was successfully synthesized through high temperature solution method for the first time. The single‐crystal X‐ray structural analysis shows that it crystallizes in the monoclinic space group C2/c (no. 15), with lattice constants a = 9.814(3) Å, b = 5.5163(15) Å, c = 13.538(4) Å, Z = 4, and β = 110.47(2)°. Its open cage‐like ∞3[Li2(P2O7)]2– framework is built up from alternating arrangement of Li2O6 and P2O7 dimers that form eight and twelve‐membered‐ring channels along the [010] direction, and the K atoms are entrapped in the larger twelve‐membered‐ring channels. Detailed structure comparisons in the N4P2O7 (N = mixed alkali metals) family are discussed. In addition, the structural validity was verified through the IR spectrum. Thermal analyses and UV/Vis/NIR diffuse reflectance spectrum are also performed on the reported compound. 相似文献
86.
磁载WO3-TiO2/SiO2/Fe3O4复合光催化剂的制备及其光催化活性 总被引:9,自引:0,他引:9
用溶胶-凝胶法在表面包覆了SiO2的磁基体Fe3O4上负载TiO2,从而得到了易于磁性固液分离的磁载WO3-TiO2/SiO2/Fe3O4复合光催化剂,并通过IR,XRD,SEM和XPS等测试手段对催化剂进行了表征.研究了磁载WO3-TiO2/SiO2/Fe3O4复合光催化剂对亚甲基蓝溶液脱色的性能,并考察了WO3掺杂量对样品催化活性的影响.结果表明,n(WO3)/n(TiO2)=0.001时,磁载WO3-TiO2/SiO2/Fe3O4复合光催化剂的催化活性最高,循环使用3次时脱色率仍保持在98%. 相似文献
87.
Jiajun Gao Pengcheng Cui Lingyun Ding Taiyi Xu Yuanlai Ju Bibo Yu Wenwu Zhang Zhilv Zhang Wei Sun 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2362-2370
The relationships between three steps of the inverse emulsion-breath figure (Ie-BF) method, including emulsion preparation, film casting and hydrophilic component loading, are explored by adjusting the experimental factors of the three implementing processes. For emulsion preparation step, the influence of the ultrasonification, the concentration of emulsifier and the addition of polymer on the size of the emulsion droplets are investigated. For film casting step, the influence of environmental humidity and several factors concerning the emulsion preparation on the porous structure of the resultant films are studied. It has been proved that high humidity is a necessity for obtaining surface pores, and multi-layered pores with disordered distribution can be formed in the bulk layer of the film when high water/oil ratio is used in making the emulsion. Bovine serum albumin is loaded into the emulsion water droplets, and by implementing the Ie-BF method under the condition of water/oil ratio being as low as 0.02 vol%, selective protein enrichment within the interior of the top-layer pores is still realized. It reflects the characteristics of “high efficiency, targeted assembly” in the step of hydrophilic component loading. 相似文献
88.
Xinyi Yang Dr. Yajun He Prof. Liuyi Li Dr. Jinni Shen Prof. Jianhui Huang Prof. Lingyun Li Prof. Zanyong Zhuang Prof. Jinhong Bi Prof. Yan Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1864-1870
Facile fabrication of nanocatalysts consisting of metal nanoparticles (NPs) anchored on a functional support is highly desirable, yet remains challenging. Covalent organic frameworks (COFs) provide an emerging materials platform for structural control and functional design. Here, a facile one-pot in situ reduction approach is demonstrated for the encapsulation of small Pd NPs into the shell of COF-derived hollow polyamine spheres (Pd@H-PPA). In the one-pot synthetic process, the nucleation and growth of Pd NPs in the cavities of the porous shell take place simultaneously with the reduction of imine linkages to secondary amine groups. Pd@H-PPA shows a significantly enhanced catalytic activity and recyclability in the tandem dehydrogenation of ammonia borane and selective hydrogenation of nitroarenes through an adsorption–activation–reaction mechanism. The strong interactions of the secondary amine linkage with borane and nitroarene molecules afford a positive synergy to promote the catalytic reaction. Moreover, the hierarchical structure of Pd@H-PPA allows the accessibility of active Pd NPs to reactants. 相似文献
89.
Dr. Jun Ying Jian-Shu Wang Lingyun Yao Dr. Wangyang Lu Prof. Dr. Xiao-Feng Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(64):14565-14569
A new procedure on palladium-catalyzed carbonylative cyclization of N-(2-pyridyl)sulfonyl (N-SO2Py)-2-iodoanilines with terminal alkenes has been developed for the rapid construction of dihydroquinolin-4(1H)-one scaffolds. Enabled by the chelating group and using benzene-1,3,5-triyl triformate (TFBen) as the CO source, both aromatic and aliphatic alkenes were smoothly transformed into the corresponding 2,3-dihydroquinolin-4(1H)-ones in good yields with excellent regioselectivities. Notably, the reaction of aromatic alkenes produces 2-aryl-2,3-dihydroquinolin-4(1H)-ones, while 3-alkyl-2,3-dihydroquinolin-4(1H)-ones were obtained when aliphatic alkenes were used. This protocol has been applied in the synthesis of antitumor agent A as well. 相似文献
90.
Lianqi Hu You Xiong Zhengrong Zou Yuanzhen Yang Junwei He Lingyun Zhong Yaqi Wang Ming Yang 《Biomedical chromatography : BMC》2020,34(8):e4849
Herb processing is a typical pharmaceutical preparation process for traditional Chinese medicine. After processing, its clinical applications and pharmacological effects vary greatly, which is most commonly attributed to the changing chemical properties between raw herb and processed products. In this work, a total of 53 chemical compounds were detected, among which 17 compounds were identified as discriminatory chemicals between raw and wine-processed Scutellaria baicalensis, and 10 components were identified as chemical markers with a cumulative content contribution of 88.75%. In addition, this work revealed that the best wine-processed time was 18 min by investigating the changes of chemical markers in S. baicalensis during processing. This work demonstrated that ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry coupled with multiple statistical strategies is an effective approach for screening and identifying discriminatory chemical markers in complex traditional Chinese medicine. 相似文献