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151.
《中国化学会会志》2018,65(5):523-530
Polyethylene glycol‐(N‐methylimidazolium) hydroxide‐grafted hydroxyapatite encapsulated γ‐Fe2O3 nanoparticles, γ‐Fe2O3@HAp@PEG(mim)OH, were prepared and characterized by FTIR, SEM, TEM, TGA, and EDAX. This nanocomposite was applied as a novel, green, nanomagnetic, and recyclable basic phase‐transfer catalyst for the synthesis of tetrahydrobenzopyrans in high yields via the three‐component reaction of aromatic aldehydes, malononitrile, and dimedone or 1,3‐cyclohexanedione in aqueous media at ambient temperature. 相似文献
152.
Reactivity Ratios and Sequence Distribution Characterization by Quantitative 13C NMR for RAFT Synthesis of Styrene‐Acrylonitrile Copolymers
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Md. Mahbub Alam Hui Peng Kevin S. Jack David J. T. Hill Andrew K. Whittaker 《Journal of polymer science. Part A, Polymer chemistry》2017,55(5):919-927
The kinetics and reactivity ratios of styrene‐acrylonitrile (SA) copolymerization have been studied extensively in bulk and in a variety of solution media using conventional free radical polymerizations (FRPs). Due to the significant difference in the two reactivity ratios for this monomer pair, at certain feed ratios the copolymers display composition drift with conversion due to monomer depletion. In this study, the kinetics of SA copolymerization using Reversible Addition‐Fragmentation Chain Transfer (RAFT) has been studied in bulk at 80 °C. The reactivity ratios for the terminal model were calculated from the comonomer sequence distributions for the RAFT process at low conversion for nine different compositions and found to be in the same range as those reported for conventional FRP of SA. The changes in the composition and sequence distribution with conversion were studied for three feed compositions. The copolymers show compositional drift with conversion, except at the azeotropic composition, and match the predictions from the reactivity ratios obtained at low conversion. From quantitative 13C NMR the triad distributions of these copolymers were estimated and found to match the predicted triad distributions as conversion increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 919–927 相似文献
153.
Bruce Bates 《Journal of Combinatorial Theory, Series A》2011,118(3):1143-1151
We define a q-analogue of the Calkin-Wilf tree and the Calkin-Wilf sequence. We show that the nth term f(n;q) of the q-analogue of the Calkin-Wilf sequence is the generating function for the number of hyperbinary expansions of n according to the number of powers that are used exactly twice. We also present formulae for branches within the q-analogue of the Calkin-Wilf tree and predecessors and successors of terms in the q-analogue of the Calkin-Wilf sequence. 相似文献
154.
陈建平 《数学建模及其应用》2015,4(3):72-74
高通量测序技术的飞速发展让生物信息领域迎来了大数据时代。新技术在提供海量生物遗传信息的同时,也给分析这些数据带来了新的挑战。DNA序列比对是信息分析流程中的关键步骤,为后续的变异检测提供序列比对信息。2015“深圳杯”数学建模夏令营B题以DNA序列比对为研究课题,希望参赛学生给出序列快速比对的最佳方案。本文简要点评了各参赛队伍的解答情况,然后介绍了现有DNA序列比对软件中用到的算法和数据结构。 相似文献
155.
Umesh C. Pant A. Dandia Hem Chandra Shweta Goyal Seema Pant 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):559-571
Abstract Two flavindogenides, 3-(2-chlorobenzylidene)-flavanone and 3-(2,4-dichloro- benzylidene)-flavanone reacted with six 5-substituted-2-aminobenzenethiols, the substituents being fluoro, chloro, bromo, methyl, methoxyl, and ethoxyl, to give respective 12 new compounds, 10-substituted-7-(2-chlorophenyl/2,4-dichlorophenyl)- 6H-6a,7-dihydro-6-phenyl[1]benzopyrano[3,4?c][1,5]benzothiazepines (5a–l) in 60–70% yields. The products were characterized on the basis of microanalytical data for elements and IR, 1 H, and 13 C NMR and mass spectral studies. All the synthesized compounds were evaluated for their antimicrobial activity against the bacteria,Escherichia coli and GFC,and the fungi,Aspergillus niger, Aspergillus flavus,and Curvularia lunata. 相似文献
156.
Franco Cataldo Giancarlo Angelini Donatella Capitani Marco Gobbino Ornella Ursini Fabrizio Forlini 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):839-849
This paper is dedicated to the memory of our friend and colleague Annalaura Segre. The chemical structure of a series of β (-)-pinene polymers (PBP) obtained by radiation-induced polymerization, free radical initiation, cationic polymerization over a Friedel-Craft catalyst and by coordinative polymerization over a Ziegler-Natta catalyst has been fully elucidated by 1H and 13C-NMR spectroscopy. 2D NMR techniques have been applied in order to assign all the NMR resonances to the structures of the PBP investigated. The NMR spectra show that the most regular PBP structure is obtained by radiation-induced polymerization followed by the free radical initiated polymerization. The most defective structure has been observed in the case of PBP prepared by cationic mechanism over a Friedel-Crafts catalyst. The discussion accounts for different types of defects and cross-links present in the PBPs investigated whose fundamental structure is based on the p-menthene repeating unit. NMR self-diffusion measurements have been performed to evaluate the molecular weight of all the PBP investigated. The highest molecular weight (2600 Dalton) was found in the case of PBP prepared by Ziegler-Natta catalyst, while the lowest molecular weight was found in the case of PBP prepared by radiation-induced polymerization (about 1000 Dalton). 相似文献
157.
Anti‐mite acrylic fiber is a new type of functional fiber which incorporates a small amount of anti‐mite agent. Basic dye can be used in the dyeing of the functional acrylic fiber. Compared with the dyeing properties of conventional fibers, the dyeing properties of the functional acrylic fiber have new characteristics such as different dyeing temperature, time, amount of leveling agent and pH level due to the rough surface and larger size of micro‐channels in the functional fiber structure that helps basic dye molecules to diffuse into the fiber. 相似文献
158.
S. Vijay Kumar T. E. Musturappa S. Prasannakumar K. M. Mahadevan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1161-1169
Free radical copolymerization of N‐vinyl‐2‐pyrrolidone with 2‐ethoxyethyl methacrylates was carried out with 2,2′‐azobisisobutyronotrile as an initiator in 1,4‐dioxane. The resulting copolymer was characterized by FTIR, H1‐NMR and C13‐NMR spectroscopic techniques thermal properties of copolymer were determined by DSC and TGA. The reactivity ratios of the monomers were computed by the Fineman‐Rose (F‐R), Kelen‐Tudos (K‐T) and extended Kelen‐Tudos (EK‐T) method at lower conversion, using the data obtained from both FTIR and elemental analysis studies; the results are in good agreement with each other. The average reactivity ratio, Alfrey‐Price Q and e values were found to be r 1=0.769, r 2=0.266 and Q 1=0.0859, e 1=0.4508, respectively for NVP/EOEMA copolymer. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on obtained reactivity ratio. The number average molecular weight and polydispersity were determined by GPC. 相似文献
159.
Xiaoying Wang Xiaobing Wang Xiaoning Wang Fentian Chen Kehui Zhu Qian Xu Meng Tang 《Analytica chimica acta》2013
A novel electrochemical biosensor based on functional composite nanofibers for sensitive hybridization detection of p53 tumor suppressor using methylene blue (MB) as an electrochemical indicator is developed. The carboxylated multi-walled carbon nanotubes (MWNTs) doped nylon 6 (PA6) composite nanofibers (MWNTs–PA6) was prepared using electrospinning, which served as the nanosized backbone for pyrrole (Py) electropolymerization. The functional composite nanofibers (MWNTs–PA6–PPy) used as supporting scaffolds for ssDNA immobilization can dramatically increase the amount of DNA attachment and the hybridization sensitivity. The biosensor displayed good sensitivity and specificity. The target wild type p53 sequence (wtp53) can be detected as low as 50 fM and the discrimination is up to 57.5% between the wtp53 and the mutant type p53 sequence (mtp53). It holds promise for the early diagnosis of cancer development and monitoring of patient therapy. 相似文献
160.
A mild and selective transition metal free protocol for the conversion of propargylic alcohols to cyclic and acyclic α,β-unsaturated enones via the Rupe rearrangement is reported. The method utilizes the Brønsted acidic ionic liquid [BMIM-SO3H][OTf] as catalyst and [BMIM][PF6] as solvent and offers the potential for recycling and reuse of the IL solvent. The feasibility to synthesize bicyclic fused cyclopentenone derivatives via a Rupe → Aldol → Nazarov sequence utilizing this protocol has also been demonstrated. 相似文献