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排序方式: 共有263条查询结果,搜索用时 15 毫秒
211.
212.
Krzysztof Matyjaszewski Mircea Teodorescu Metin H. Acar Kathryn L. Beers Simion Coca Scott G. Gaynor Peter J. Miller Hyun‐jong Paik 《Macromolecular Symposia》2000,157(1):183-192
Transformation of different living and non‐living polymerization mechanisms to controlled/“living” atom transfer radical polymerization (ATRP) in order to prepare block and graft copolymers is described. The synthesis and characterization of macroinitiators and the resulting segmented copolymers is discussed. 相似文献
213.
Byung Kyu Kim Sang Hyun Paik 《Journal of polymer science. Part A, Polymer chemistry》1999,37(15):2703-2709
Poly(ethylene glycol) (PEG) with molecular weight (Mn) of 1000, 2000, 3000, and 4000 g/mol, four types of diisocyanate [hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (H12MDI), isophorone diisocyanate (IPDI), and toluene diisocyanate (TDI)], two types of comonomers [acrylamide (AAm) and acrylic acid (AAc)] that comprised up to 60% of the total solid were used to prepare UV-curable PEG–based polyurethane (PU) acrylate hydrogel. The gels were evaluated in terms of mechanical properties, water content as a function of immersion time and pH, and X-ray diffraction profiles of dry and swollen films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2703–2709, 1999 相似文献
214.
Sang-Won Lee Jong-Min Lim Seong-Hee Bhoo Young-Sook Paik Tae-Ryong Hahn 《Analytica chimica acta》2003,480(2):267-274
Genipin, a hydrolysate of geniposide from gardenia fruits, produces blue pigments on reaction with amino acids. The colorimetric detection of amino acids using this genipin reaction was evaluated and compared with the well-known ninhydrin reaction. The molar absorptivities of the blue pigments, the reaction products of genipin with various amino acids, were greater than those of the respective ninhydrin reaction products. When asparagine was reacted with genipin, the molar absorptivity was about 14 times higher than with ninhydrin. The absorbance of the genipin–amino acids increased linearly with increase of amino acid concentration, indicating that genipin could be a useful reagent for quantitation of amino acids. Thin layer chromatographic analysis showed that the genipin reaction produces clear and stable colored spots. The blue ninhydrin reaction spots were usually bleached in 24 h at room temperature, while the genipin reaction spots remained unchanged for several months. The addition of 0.1 mM Cu2+ and Fe3+ decreased the absorbance of Gly–ninhydrin pigment by 50% and 98%, respectively, but those metal ions did not affect the absorbance of the Gly–genipin pigment. 相似文献
215.
Hye Jin Choi Taek Soon Lee Myunghyun Paik Suh 《Angewandte Chemie (International ed. in English)》1999,38(10):1405-1408
A three-dimensional network with one-dimensional channels (see picture) has been self-assembled from the nickel(II ) complex of cyclam and 1,3,5-benzenetricarboxylate in water through hydrogen-bond formation. The channels have an appropriate diameter (10.3 Å) to include D -glucose with a formation constant of Kf=(1.38±0.01)×104 M −1. Under similar conditions maltose is not included. 相似文献
216.
Edward-Sam Edwin Prabhakaran Vasantha-Srinivasan Sengottayan Senthil-Nathan Muthiah Chellappandian Sengodan Karthi Radhakrishnan Narayanaswamy Vethamonickam Stanley-Raja Haridoss Sivanesh Ramakrishnan Ramasubramanian Asma A. Al-Huqail Faheema Khan Patcharin Krutmuang Ahmed Abdel-Megeed Aml Ghaith Chae-Hoon Paik 《Molecules (Basel, Switzerland)》2021,26(19)
Spodoptera litura Fab. is a polyphagous pest causing damage to many agriculture crops leading to yield loss. Recurrent usage of synthetic pesticides to control this pest has resulted in resistance development. Plant-derived diterpenoid compound andrographolide was isolated from the leaves of Andrographis paniculata. It was analysed by gas chromatography-mass spectroscopy and quantified by HPLC. Nutritional indices and digestive enzymatic profile were evaluated. Third, fourth and fifth instar larvae were treated with different concentrations of andrographolide. At 3, 6 and 9 ppm-treated concentrations the larvae showed decreased RGR, RCR, ECI, ECD values with adverse increase in AD. The digestive enzymes were significantly inhibited when compared with control. Conspicuously, andrographolide showed pronounced mortality of S. litura by inhibition of enzyme secretion and intake of food. The binding ability of andrographolide with CYTP450 showed high affinity with low binding energy. Andrographolide has the potential to be exploited as a biocontrol agent against S. litura as an eco-friendly pesticide. 相似文献
217.
Simultaneous analysis of seven 2‐hydroxy fatty acids as tert‐butyldimethylsilyl derivatives in plasma by gas chromatography–mass spectrometry
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Chan Seo Jaehwan Yoon Yumie Rhee Jong‐Jin Kim Sang‐Jip Nam Wonjae Lee Gwang Lee Sung‐Tae Yee Man‐Jeong Paik 《Biomedical chromatography : BMC》2015,29(1):156-160
An efficient method for the simultaneous analysis of seven 2‐hydroxy fatty acids (2‐HFAs) as tert‐butyldimethylsilyl (TBDMS) derivative was developed by gas chromatography–mass spectrometry in selected ion monitoring mode. New mass spectral data on 2‐hydroxycapric, 2‐hydroxypalmitic, 2‐hydroxystearic and 2‐hydroxybehenic acids as di‐TBDMS derivatives for hydroxyl and carboxyl groups were built. Under the optimal conditions, the present method showed a good correlation coefficient (r ≥ 0.999) in the range of 0.01–0.5 µg. The precision showed low relative standard deviation of <10%, and the accuracy (percentage relative error) varied from ?5.2 to 0.3 for the seven 2‐HFAs studied. Recovery rates of all 2‐HFAs were ≥ 93.2% with good precision. When applied to normal human plasma, seven 2‐HFAs were positively identified. Therefore, the present efficient method will be useful for simultaneous analysis of 2‐HFAs in plasma. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
218.
Pure single-phase Li2MnSiO4 nanoparticle-embedded carbon nanofibers have been prepared for the first time via a simple sol-gel and electrospinning technique. They exhibit an improved electrochemical performance over conventional carbon-coated Li2MnSiO4 nanoparticle electrodes, including a high discharge capacity of ~200 mAh g?1, at a C/20 rate, with the retention of 77 % over 20 cycles and a 1.6-fold higher discharge capacity at a 1 C rate. 相似文献
219.
Enhancing CO2 Separation Ability of a Metal–Organic Framework by Post‐Synthetic Ligand Exchange with Flexible Aliphatic Carboxylates
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Dae Ho Hong Prof. Myunghyun Paik Suh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):426-434
A series of porous metal–organic frameworks having flexible carboxylic acid pendants in their pores (UiO‐66‐ADn: n=4, 6, 8, and 10, where n denotes the number of carbons in a pendant) has been synthesized by post‐synthetic ligand exchange of terephthalate in UiO‐66 with a series of alkanedioic acids (HO2C(CH2)n?2CO2H). NMR, IR, PXRD, TEM, and mass spectral data have suggested that a terephthalate linker in UiO‐66 was substituted by two alkanedioate moieties, resulting in free carboxyl pendants in the pores. When post‐synthetically modified UiO‐66 was partially digested by adjusting the amount of added HF/sample, NMR spectra indicated that the ratio of alkanedioic acid/terephthalic acid was increased with smaller amounts of acid, implying that the ligand substitution proceeded from the outer layer of the particles. Gas sorption studies indicated that the surface areas and the pore volumes of all UiO‐66‐ADns were decreased compared to those of UiO‐66, and that the CO2 adsorption capacities of UiO‐66‐ADn (n=4, 8) were similar to that of UiO‐66. In the case of UiO‐66‐AD6, the CO2 uptake capacity was 34 % higher at 298 K and 58 % higher at 323 K compared to those of UiO‐66. It was elucidated by thermodynamic calculations that the introduction of flexible carboxyl pendants of appropriate length has two effects: 1) it increases the interaction enthalpy between the host framework and CO2 molecules, and 2) it mitigates the entropy loss upon CO2 adsorption due to the formation of multiple configurations for the interactions between carboxyl groups and CO2 molecules. The ideal adsorption solution theory (IAST) selectivity for CO2 adsorption over that of CH4 was enhanced for all of the UiO‐66‐ADns compared to that of UiO‐66 at 298 K. In particular, UiO‐66‐AD6 showed the most strongly enhanced CO2 uptake capacity and significantly increased selectivity for CO2 adsorption over that of CH4 at ambient temperature, suggesting that it is a promising material for sequestering CO2 from landfill gas. 相似文献
220.
Suk Yong Jung Jung Mo Moon Soo Chool Lee Sang Cheol Paik Ki Soo Park Jae Chang Kim 《Adsorption》2014,20(2-3):341-348
Dimethyl disulfide (DMDS) and dimethyl sulfide (DMS) are non-polar, stable, organic sulfur compounds found in liquefied petroleum gas, and their oxidation in the atmosphere results in the formation of tropospheric sulfur dioxide, which is subsequently converted into sulfuric acid, as the main factor of acid rain. In the present study, adsorption processes were devised based on the use of modified zeolite impregnated with rare-earth metals (Ce, La or Pr) for the adsorption of DMDS and DMS, and their sorption capacities were compared with that of commercial zeolite [Zeolite-Y, Ultra Stable Y(USY)]. The adsorption capacities of adsorbents were tested using a micro liquid flow reactor at room temperature. USY impregnated with cerium oxide (UC-10) had excellent DMDS and DMS adsorption capacities as compared with the other adsorbents tested. It was found that impregnation of USY with rare-earth metal such as Ce improved the sulfur adsorption capacity of zeolite. The form of the Ce promoter impregnated into USY was determined by FT-Raman spectroscopy. Adsorbents were characterized by X-ray fluorescence spectrometer, X-ray diffraction, and BET and the results obtained are discussed. 相似文献