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991.
A new method for the simultaneous determination of anions (sulfate, nitrate, and chloride) and cations (sodium, ammonium, potassium, magnesium, and calcium) in acid rain waters was investigated using high-performance ion-exclusion/cation-exchange chromatography with conductimetric detection on a separation column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the hydrogen-form and an eluent comprising 1.5 mM sulfosalicylic acid–6 mM 18-crown-6 at pH 2.6, operated at 1.5 ml/min. Effective separation and highly sensitive conductimetric detection for the anions and the cations was achieved in about 14 min. Since the ionic balance (equivalents of anions/equivalents of cations) of acid rain waters of different pH (4.40–4.67) ranged from 0.97 to 0.94, evaluation of the water quality of acid rain was possible. This method was successfully applied to the simultaneous determination of the anions and the cations in acid rain transported from mainland China and North Korea to central Japan monitored by a meteorological satellite data analyzer. 相似文献
992.
Timothy W. Strohmeyer D. Robert Sliskovic S. A. Lang Yang-I Lin 《Journal of heterocyclic chemistry》1985,22(1):7-10
Reactions of monothiodiacylamines or N-aroylthioimidates with 3-aminopyrazoles gave pyrazolo[1,5-a]-1,3,5-triazines in good yields. 相似文献
993.
This paper presents systematic investigation of the microchannel surface properties in microCE chips. Three popular materials for microCE chips, polydimethylsiloxane (PDMS), quartz, and glass, are used. The zeta potentials of these microchannels are calculated by measuring the EOF velocity to evaluate the surface properties after surface modification. The hydrophobic PDMS is usually plasma-treated for microCE applications. In this study, a new method using a high-throughput atmospheric plasma generator is adopted to treat the PDMS surface under atmospheric conditions. In this approach, the cost and time for surface treatment can be significantly reduced compared with the conventional vacuum plasma generator method. Experimental results indicate that new functional groups could be formed on the PDMS surface after treatment, resulting in a change in the surface property. The time-dependent surface property of the plasma-treated PDMS is then measured in terms of the zeta potential. Results show that the surface property will reach a stable condition after 1 h of plasma treatment. For glass CE chips, two new methods for changing the microchannel surface properties are developed. Instead of using complicated and time-consuming chemical silanization procedures for CE channel surface modification, two simple and reliable methods utilizing organic-based spin-on-glass and water-soluble acrylic resin are reported. The proposed method provides a fast batch process for controlling the surface properties of glass-based CE channels. The proposed methods are evaluated using PhiX-174 DNA maker separation. The experimental data show that the surface property is modified and separation efficiency greatly improved. In addition, the long-term stability of both coatings is verified in this study. The methods proposed in this study show potential as an excellent solution for glass-based microCE chip surface modification. 相似文献
994.
Study on microstructure and mechanical properties relationship of short fibers/rubber foam composites 总被引:1,自引:0,他引:1
Research on short fibers/rubber foam composites is rarely found in the literature. In this paper, microcellular rubber foams unfilled (MF), strengthened by pretreated short fibers (MFPS) and untreated short fibers (MFUS) are prepared, respectively. The microstructure and mechanical properties of the three composites have been studied via scanning electron microscope (SEM) and mechanical testing, respectively. The SEM results show that both pretreated and untreated short fibers disperse uniformly in the composites and in bidimensional orientation. Moreover, the pretreated short fibers have much better adhesion with the rubber matrix than untreated ones. The experimental results also indicate that the introduction of short fibers is mainly responsible for the great enhancement of most mechanical properties of the microcellular rubber foams, and the good interfacial adhesion of the short fibers with the matrix contributes to the more extensive improvement in the mechanical properties. It is also found that the reinforcement effect of short fibers to compressive modulus strongly depends on the density of microcellular rubber foams, the orientation of short fiber and the deformation ratio. The compressive modulus of microcellular rubber foams at the normalized density less than 0.70 and beyond 0.70 is predicted by the modified Simple Blending Model and the Halpin-Kerner Model, respectively. The theoretically predicted values are in good accordance with the experimental results. 相似文献
995.
A new dihydrobenzodioxane derivative, origalignanol ( 10 ), together with nine polyphenolic compounds, salvianolic acid A ( 1 ), salvianolic acid C ( 2 ), lithospermic acid ( 3 ), apigenin 7‐O‐β‐D‐glucuronide ( 4 ), apigenin 7‐O‐β‐D‐(6″‐methyl)glucuronide ( 5 ), luteolin, ( 6 ), luteolin 7‐O‐β‐D‐glucopyranoside ( 7 ), luteolin 7‐O‐β‐D‐glucuronide ( 8 ), and luteolin 7‐O‐β‐D‐xylopyranoside ( 9 ), were isolated from the aqueous ethanolic extract of the aerial parts of Origanum vulgare for the first time. The structure of new compound 10 was determined on the basis of spectroscopic methods. Compound 5 is probably an artifact formed during the isolation. Compounds 1, 2 and 3 showed strong DPPH radical scavenging activity with an EC50 of 7.2 ± 0.4, 9.6 ± 0.9, and 9.5 ± 0.7 μM, respectively, and protected rat hepatocytes from CCl4‐damage at 100 μM. 相似文献
996.
A new program to characterize polyethylene glycol-modified (PEGylated) proteins is outlined using capillary zone electrophoresis (CZE). PEGylated ribonuclease A and lysozyme were selected as examples. Five separation procedures were compared to select out the mixed buffer of acetonitrile-water (1:1, v/v) at pH 2.5 as the best to characterize the PEGylated proteins without sample pretreatment. Polyethylene oxide (PEO) with a high molecular mass of 8 x 10(6) was applied to rinse the capillary to form a dynamic coating which would decrease the undesirable proteins adsorbed to the inner wall of the silica. The electroosmotic flow (EOF) mobility of the five procedures was determined, respectively. It is found that acetonitrile is mainly responsible for the good resolution of PEGylated proteins with the help of PEO coating in the semi-aqueous system. The low EOF mobility and current in the semi-aqueous system might also have some responsibility for the high resolution. The semi-aqueous procedure described in this paper also demonstrates higher resolution of natural proteins than aqueous ones. 相似文献
997.
A novel three-dimensional metal selenite [Fe2(H2O)4(SeO3)2] (1) has been hydrothermally synthesized and characterized by the elemental analyses, IR spectrum, TG analysis and the single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P21/n, with a=6.5283(13) Å, b=8.8754(18) Å, c=7.6798(15) Å, (=98.82(3)β, V=439.71(15) Å3, and Z=2. Compounds 1 exhibits interesting three-dimensional structure constructed from {FeO6} octahedra and {SeO3} pyramids linked via the corner- and/or edge-sharing mode. The most interesting structural feature of compound 1 is that the existence of multidirectional intersecting double helical chains in one compound. 相似文献
998.
Three new coumarins, yuehgesin-A (1), -B (2) and -C (3) and 22 compounds—murracarpin (4), mupanidin (5), isomeranzin (6), murralongin (7), scopoletin (10), 7-methoxy-8-(l′-ethoxy-2′-hydroxy-3′-methyl-3′-butenyl)coumarin (11), umbelliferone (12), paniculatin (13), braylin (14), auraptenol (15), meranzin hydrate (16), minumicrolin (17), scopolin (18), caffeine (19), 3,3′,4′,5,5′,6,7-heptamethoxyflavone (20), 4-hy-droxybenzaldebyde (21), p-hydroxybenzoic acid (22), cis- and trans-ferulic acid (23), cis- and transmethyl ferulate (24) and trans-ethylferulate (25)—were isolated and characterized from fresh flowers of Murraya paniculata collected in Taiwan. Their structures were elucidated by spectral methods. The chemotaxonomy of Murraya paniculata is, discussed. 相似文献
999.
Wen Lu Qin‐Yu Zhu Yong Zhang Xiao‐Min Lin Jie Dai 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):m496-m498
The title salt, bis[2,3‐bis(aminocarbonyl)‐8,9‐bis(methylsulfanyl)tetrathiafulvalenium] di‐μ‐bromido‐bis[bromidocopper(II)], (C10H10N2O2S6)2[Cu2Br4], contains 2,3‐bis(aminocarbonyl)‐8,9‐bis(methylsulfanyl)tetrathiafulvalenium radical cations, [DMT‐TTF(CONH2)2]·+, and [Cu2Br4]2− anions. The cations are associated across centres of inversion in a head‐to‐tail fashion via short face‐to‐face S...S stacking (TTF moiety). These dimers are further assembled into a one‐dimensional chain structure via interdimer double S...S contacts involving the methylsulfanyl groups. The one‐dimensional chains give rise to a two‐dimensional structure through intermolecular double N—H...O hydrogen bonds involving the amide group. The [Cu2Br4]2− anions, which straddle centres of inversion, are located between the cation layers. Electron paramagnetic resonance measurements show a radical signal, indicating that the two TTF·+ radicals are not completely coupled in the dimer. 相似文献
1000.
Yu-Xi Sun Ran Zhang De-Jun Ding Shu Liu Bao-Lin Wang Yan-Li Wang Yong-Xiang Lin 《Structural chemistry》2006,17(6):655-665
The Schiff base compounds, 4-(2-hydroxy-5-nitr- obenzylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpy- razol-3-one and 4-(3-bromo-5-chloro-2-hydroxybenz-
ylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one, have been synthesized and characterized by elemental analysis,
IR, and X-ray single crystal determination. Density functional calculations of the structures, natural bond orbitals, and
frontier molecular orbitals and Mülliken charge analysis on the compounds were performed at B3LYP/6-31+G(d) level of theory.
Vibrational frequencies were also predicted, assigned, and compared with the experimental values, which supported each other. 相似文献