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991.
A sensitive GC–MS method has been established for the determination of acrylamide in surface and drinking water based on derivatization with xanthydrol. Deuterated acrylamide (acrylamide‐d3) was chosen as the internal standard for analyzing the water sample. The derivatization of acrylamide was performed directly in water, and the best reaction conditions (xanthydrol of 1.6 mM, HCl concentration of 0.05 M, reaction for 30 min at ambient temperature) were established by variation of parameters. Under the established conditions, the detection and quantification limits were 3.0 and 9.7 ng/L, respectively, and the interday RSD was less than 8% at concentrations of 20 and 100 ng/L. 相似文献
992.
Yamei Li Yoo Kyung Go Hideshi Ooka Daoping He Fangming Jin Sun Hee Kim Ryuhei Nakamura 《Angewandte Chemie (International ed. in English)》2020,59(24):9744-9750
Nitrate is a pervasive aquatic contaminant of global environmental concern. In nature, the most effective nitrate reduction reaction (NRR) is catalyzed by nitrate reductase enzymes at neutral pH, using a highly‐conserved Mo center ligated mainly by oxo and thiolate groups. Mo‐based NRR catalysts mostly function in organic solvents with a low water stability. Recently, an oxo‐containing molybdenum sulfide nanoparticle that serves as an NRR catalyst at neutral pH was first reported. Herein, in a nanoparticle‐catalyzed NRR system a pentavalent MoV(=O)S4 species, an enzyme mimetic, served as an active intermediate for the NRR. Potentiometric titration analysis revealed that a redox synergy among MoV?S, S radicals, and MoV(=O)S4 likely play a key role in stabilizing MoV(=O)S4, showing the importance of secondary interactions in facilitating NRR. The first identification and characterization of an oxo‐ and thiolate‐ligated Mo intermediates pave the way to the molecular design of efficient enzyme mimetic NRR catalysts in aqueous solution. 相似文献
993.
994.
Nguyen Thi Minh Hien Joo Hee Chung Xiang‐Bai Chen Woo Jun Kwon Chul Sung Kim In‐Sang Yang 《Journal of Raman spectroscopy : JRS》2015,46(11):1161-1165
LiFe1 − xMnxPO4 olivines are promising material for improved performance of Li‐ion batteries. Spin–phonon coupling of LiFe1 − xMnxPO4 (x = 0, 0.3, 0.5) olivines is studied through temperature‐dependent Raman spectroscopy. Among the observed phonon modes, the external mode at ~263 cm−1 is directly correlated with the motions of magnetic Fe2+/Mn2+ ions. This mode displays anomalous temperature‐dependent behavior near the Néel temperature, indicating a coupling of this mode with spin ordering. As Mn doping increases, the anomalous behavior becomes clearly weaker, indicating the spin–phonon coupling quickly decreases. Our analyses show that the quick decrease of spin–phonon coupling is due to decrease of the strength of spin–phonon coupling, but not change of spin‐ordering feature with Mn doping. Importantly, we suggest that the low electrochemical activity of LiMnPO4 is correlated with the weak spin–phonon coupling strength, but not with the weak ferromagnetic ground state. Our work would play an important role as a guide in improving the performances of future Li‐ion batteries. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
995.
Novel pH-sensitive hydrogels were prepared by grafting β-cyclodextrin (βCD) to polyethyleneimine (PEI) and cross-linking βCD using epichlorohydrin (EPI). While the molar ratio of βCD to PEI was kept to 1:50, the molar ratio of EPI to βCD was varied so that it was 3/1, 5/1, and 10/1. When the EPI to βCD ratio was higher, the degree of equilibrium swelling and the percentage release were lower, possibly due to a higher cross-linking density. The % release of blue dextran was much less than that of fluorescein isothiocyanate-dextran (FITC-dextran). The electrostatic interaction of blue dextran with the hydrogel is believed to suppress the release of the dye. Among the hydrogels prepared in this work, the hydrogel prepared using the βCD to EPI ratio of 1/5 was the most pH sensitive in terms of the degree of swelling and the degree of FITC-dextran release. 相似文献
996.
Kwan Soo Kim Yeong Hee Ahn Suk Bong Park In Haeng Cho Yung Hyup Joo Byoung Hee Youn 《Journal of carbohydrate chemistry》2013,32(5):911-915
Additions of organometallics to chiral α-alkoxy and α,β-dialkoxy carbonyl compounds have recently attracted a great deal of attention since this methodology has a great potential for the synthesis of a variety of polyoxy natural products such as macrolide antibiotics and polyether ionophores. Interpretation of the stereochemical outcome of the addition of organometallics to α,β-dialkoxy carbonyls, however, is rather complex and inconclusive1 compared to that of α-alkoxy carbonyls.2. 相似文献
997.
It is shown that a Banach space X has Fourier type p with respect to a locally compact abelian group G if and only if the dual space X′ has Fourier type p with respect to G if and only if X has Fourier type p with respect to the dual group of G. This extends previously known results for the classical groups and the Cantor group to the setting of general locally compact
abelian groups.
Supported by DFG grant Hi 584/2-2.
Partially supported by a DAAD-grant A/02/46571. 相似文献
998.
999.
Mohammad Rezaul Karim Kwon Taek Lim Chul Jae Lee Md Tauhidul Islam Bhuiyan Hee Jin Kim Lee‐Soon Park Mu Sang Lee 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5741-5747
Core‐shell silver (Ag)–polyaniline (PAni) nanocomposites have been synthesized by the in‐situ gamma radiation‐induced chemical polymerization method. Aqueous solution of aniline, a free‐radical oxidant, and/or silver metal salt were irradiated by γ‐rays. Reduction of the silver salt in aqueous aniline leads to the formation of silver nanoparticles which in turn catalyze oxidation of aniline to polyaniline. The resultant Ag‐PAni nanocomposites were characterized by using different spectroscopy analyses like X‐ray photoelectron, UV–visible, and infrared spectroscopy. The optical absorption bands revealed that the bands at about 400 nm are due to the presence of nanosilver and the blue‐shifted peak at ~ 555 nm is due to the presence of metallic silver within the PAni matrix. X‐ray diffraction pattern clearly indicates the broad amorphous polymer and the sharp metal peaks. Scanning electron microscopy and transmission electron microscopy of the nanocomposite showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the composites have a higher degradation temperature than polyaniline alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5741–5747, 2007 相似文献
1000.
Quantum analogues ofn-dimensional balls are defined via suitable generators and relations. In the even case they correspond to the Twisted Canonical Commutation Relations of Pusz and Woronowicz. Then we construct quantum spheres as double manifolds of the noncommutative balls. 相似文献