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101.
Der‐Lii M. Tzou Lin‐Kai Ni Mei‐Man Chen Min‐Chuan Chiou Li‐Chou Chen Shan‐Te Hsu Kuo‐Lung Ku Chien‐Chung Cheng 《中国化学会会志》2013,60(9):1107-1112
Solid‐state Nuclear Magnetic Resonance (ss‐NMR) 13C single‐pulse excitation spectroscopy in combination with the magic‐angle spinning (MAS) technique was applied to a series of Phalaenopsis tissues, including the leaf, sheath, stem, and root, at different growth and spiking periods. Compared with{1H}/13C cross‐polarization MAS spectra, the 13C single‐pulse excitation MAS spectra displayed very distinct spectral patterns, recognizable as fingerprints of the tissues studied. 1Here, we demonstrate that solid‐state 13C single‐pulse excitation NMR spectroscopy provides a direct and robust analytical tool for studying the various tissues of Phalaenopsis in different growth and spiking induction periods. 相似文献
102.
In this study, porous TiO2 thin films were prepared by the sol‐gel method employing polyethylene glycol 1000 (PEG 1000) as an organic template. Pore sizes were adjusted by varying the concentration of PEG 1000. The optimal PEG concentration range required to form TiO2 films with a regular porous structure was investigated and was found to be 0.01–0.015 M. As the PEG 1000 concentration increased, the surface of these films became rougher because of larger pores. Degradation of methylene blue (MB) under UV irradiation was used to determine the photocatalytic activity of the films. In addition, the effect of the pH value of the MB solution on the films was evaluated by controlling its pH value at 5, 7, and 9. The results showed that the photocatalytic activity was correlated to the pore size and pore density of the thin films. TiO2 thin films possessing pore sizes in the diameter range of 35–85 nm exhibited the best conversion of 98% after 8 h of UV irradiation when the pH value was 7. 相似文献
103.
Epoxy composites were prepared using diglycidyl ether bisphenol F and water-dilutable diglycidyl ether bisphenol A with curing agents, polyoxypropylenediamine and diethylmethylbenzenediamine, in water or dimethylformamide as a solvent. The influence of cellulose nanofibers and solvents on curing kinetics of epoxy composites was investigated. Curing kinetic parameters were calculated using the model-fitting methods and the isoconversional method. Among these, the Sestak–Berggren equation best fit the experimental data. Results indicated that dimethylformamide decreased the reaction rate, whereas water revealed the opposite pattern. Cellulose nanofibers catalyzed the reaction between bisphenol F resins and the aromatic curing agent. 相似文献
104.
C. L. Kuo T. L. Tsai A. C. Chiang K. S. Chang-Liao J. H. Chao 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):465-473
The purpose of this study is to develop a neutron activation method to determine trace amounts of 129I in cement-solidified radwastes. The radwaste samples were alkaline fused using KOH and then 129I and iodine carrier were chemically separated by solvent extraction before and after neutron irradiation. Both stable iodine (127I) and 129I can be activated by neutrons through 127I (n, 2n) 126I and 129I (n, γ) 130I reactions; their activated radionuclides were counted together with a high-purity germanium detector. The chemical recovery yields ranged from 30 to 60 %, and it was found that more than 99.9 % of interfering radionuclides can be removed using solvent extraction after neutron irradiation. The minimum detectable amounts can be lowered to less than 1 mBq g?1, which is superior to low energy γ-ray spectrometry by a factor of >102, on average. The established technique can be applied to re-evaluation of 129I content in radwastes that can be re-classified to lower classes, and the cost for designing a final disposal facility can be significantly reduced. 相似文献
105.
A homologous series of 4,4'-bis(omega-hydroxyalkoxy)-alpha-methylstilbenes, denoted HAMS-n, has been synthesized. Here n is the carbon atom length of the peripheral n-alkyl chain; in this work n = 2 to 8 and 11. The composition, microstructure, thermal properties, and mesomorphism of the homologues were determined using elemental analysis, 1H NMR, FTIR, DSC, wide angle X-ray diffraction, and polarizing optical microscopy with a heating stage. The influence of the length and the even/odd numbers of methylene units of the peripheral chains on the variants of mesomorphism and the stability of mesophases, as well as on their transition temperatures, are discussed. The homologues with n = 8 and 11 were enantiotropic monomorphic, CrG (or CrH). The odd homologues showed monotropic trimorphism on cooling, while the even homologues exhibited enantiotropic trimorphism. A pronounced even/odd effect on the melting temperatures was observed. 相似文献
106.
应用拉曼光谱技术研究了焦磷酸钾、硝酸钾、磷酸二氢钾、乙二胺四乙酸钠等十余种可溶性盐水溶液以及它们的混合物溶液的拉曼光谱特征,考察了共存组分对焦磷酸根拉曼光谱特征峰的影响;建立了基于拉曼光谱技术定量分析溶液中焦磷酸根离子含量的方法。结果表明,以硝酸钾为内标物,保持被测溶液pH 11,焦磷酸根离子拉曼光谱特征峰强度与硝酸根离子拉曼光谱特征峰强度之比值对焦磷酸根浓度呈良好的线性关系,所得线性回归方程为y=1.2110x+0.1515,相关系数R2=0.9996;已经研究过的十余种可溶性盐共存物几乎不干扰焦磷酸根离子的定量分析。 相似文献
107.
Ya‐Chu Hsieh Hau‐Yu Fang Yi‐Ting Chen Rong Yang Chen‐I Yang Pi‐Tai Chou Ming‐Yu Kuo Yao‐Ting Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(10):3112-3116
The syntheses, structures, and physical properties of dibenzozethrenes were explored. The results thus obtained were compared with those for zethrenes. Dibenzozethrenes were synthesized by the nickel‐catalyzed cyclodimerization of 9‐ethynyl‐1‐iodoanthracenes. The substituents in zethrene and dibenzozethrene twisted their backbones, and remarkably influenced their properties. Unlike closed‐shell disubstituted derivatives, the parent zethrene and dibenzozethrene are singlet open‐shell biradicals, which were studied by variable‐temperature 1H NMR, ESR, SQUID and computational methods. Since substituents were observed to affect significantly the biradical properties, the relevant mechanisms were analyzed. The nonlinear optical performance of each of these compounds depends on its π‐conjugation and biradical properties. Dibenzozethrenes have larger two‐photon absorption cross‐sections than zethrenes, as most strongly evidenced by the parent dibenzothrene [σmax=4323 GM at 530 nm]. 相似文献
108.
Deepak Kumar Barange Veerababurao KavalaChun-Wei Kuo Cheng-Chuan WangR.R. Rajawinslin Janreddy DonalaChing-Fa Yao 《Tetrahedron》2014
An efficient regioselective synthesis of 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide derivatives via iodocyclization approach using iodine under mild reaction condition described herein. This coupling–iodocyclization strategy tolerated a variety of functional groups such as alkyl, cycloalkyl, phenyl producing the six-membered heterocyclic ring selectively. The resulting 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide was coupled with a variety of boronic acids (Suzuki coupling) and activated alkenes (Heck coupling). The iodo group was utilized for Sonogashira coupling followed by efficient transformation to azido precursor, which was used for the synthesis of various thieno-sultam linked with triazole. 相似文献
109.
On the Size Evolution of Monolayer‐Protected Gold Clusters during Ligand Place‐Exchange Reactions: The Effect of Solvents 下载免费PDF全文
Dr. Chun‐Ting Kuo Chiu‐Feng Chen Meng‐Wen Gu Man‐Nung Su Jhih‐Fong Huang Dr. Min‐Jie Huang Prof. Chun‐hsien Chen 《化学:亚洲杂志》2014,9(3):844-851
Ligand place‐exchange (LPE) reactions are extensively applied for the post‐functionalization of monolayer‐protected gold clusters (MPCs) by using excessive incoming ligands to displace initial ones. However, the modified MPCs are often enlarged or degraded; this results in ill‐defined size‐dependent properties. The growth of MPCs essentially involves an unprotected surface that is subsequently has gold atoms added or is fused with other gold cores owing to collision. Reported herein is a guideline for the selection of solvents to suppress unwanted MPC growth. Favorable solvents are those with significant affinity to gold or with low solubility for desorbed ligands because these properties retard LPE reactions and minimize the time available for unprotected gold cores. This finding provides a general and convenient approach to regulate the size of functionalized MPCs. 相似文献
110.
Chang Chi-I Chen Cheng-Chi Ko Horng-Huey Chen Jih-Jung Cheng Ming-Jen Chao Che-Yi Kuo Yueh-Hsiung 《Chemistry of Natural Compounds》2022,58(3):478-481
Chemistry of Natural Compounds - A new seco-abietanoid, 12-methoxy-7-oxo-6,7-secoabieta-8,11,13-trien-6-oic acid (1), and a known seco-abietanoid,12-hydroxy-6,7-secoabieta-8,11,13-triene-6,7-dial... 相似文献