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891.
本文提出了一个硫酸中间盐子循环用以代替分解水制氢的KNO_3-I_2混合循环中的电解反应,从而使原混合循环变为一个纯热化学循环。 相似文献
892.
Biosorption of copper(II) and zinc(II) from aqueous solution by Pseudomonas putida CZ1 总被引:1,自引:0,他引:1
Chen XC Wang YP Lin Q Shi JY Wu WX Chen YX 《Colloids and surfaces. B, Biointerfaces》2005,46(2):101-107
To study Pseudomonas putida CZ1, having high tolerance to copper and zinc on the removal of toxic metals from aqueous solutions, the biosorption of Cu(II) and Zn(II) by living and nonliving P. putida CZ1 were studied as functions of reaction time, initial pH of the solution and metal concentration. It was found that the optimum pH for Zn(II) removal by living and nonliving cells was 5.0, while it was 5.0 and 4.5, respectively, for Cu(II) removal. At the optimal conditions, metal ion biosorption was increased as the initial metal concentration increased. The adsorption data with respect to both metals provide an excellent fit to the Langmuir isotherm. The binding capacity of living cells is significantly higher than that of nonliving cells at tested conditions. It demonstrated that about 40-50% of the metals were actively taken up by P. putida CZ1, with the remainder being passively bound to the bacterium. Moreover, desorption efficiency of Cu(II) and Zn(II) by living cells was 72.5 and 45.6% under 0.1M HCl and it was 95.3 and 83.8% by nonliving cells, respectively. It may be due to Cu(II) and Zn(II) uptake by the living cells enhanced by intracellular accumulation. 相似文献
893.
Density functional theory has been applied at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level to examine the energetics of alpha,beta- versus beta,gamma-unsaturation for some common organic functional groups. Specifically, the relative stabilities of allyl-X (H2C=CHCH2X) and 1-propenyl-X (H3CCH=CHX) isomers have been computed for X = methyl, vinyl, phenyl, formyl, acetyl, methoxy, methylthio, methylsulfinyl, methylsulfonyl, sulfamoyl, and methoxysulfonyl, and the results are compared to available experimental data. The intrinsic preference of 3 kcal/mol for the 1-propenyl isomer when X = CH3 is exceeded by 2-4 kcal/mol for first-row conjugating groups, but it is not met for the sulfur-containing groups. In particular, alpha,beta-unsaturation is favored by less than 1 kcal/mol for the sulfone and sulfonamide analogues, while it is preferred by 8 kcal/mol for the vinyl-substituted case. Detailed structural results and torsional energy profiles are also reported. 相似文献
894.
Changzheng Wu Qing Yang Chao Huang Ping Yin Yi Xie 《Journal of solid state chemistry》2004,177(10):3522-3528
Pure hexagonal aluminum nitride (AlN) nanowhiskers have been successfully synthesized by directly reacting AlCl3 with NaN3 in non-solvent system at the low temperature of 450 °C for 24 h. The obtained products are characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and selected area electron diffraction, which show that the obtained products are hexagonal phase AlN nanowhiskers with width from 10 to 80 nm and length up to several micrometers. The influencing factors of the formation of AlN nanowhiskers were discussed and a possible growth mechanism for AlN nanowhiskers was proposed. Additionally, the study on the corresponding optical properties and catalytic properties is also carried out. 相似文献
895.
The stabilization modification of the halogen end groups of polystyrene prepared by atom transfer radical polymerization (ATRP) has been attempted. The reaction mechanism adopted is radical chain transfer reaction, and iso-propylbenzene is employed as not only the chain transfer agent but also the solvent. Moreover, Cu0 is used as the acceptor of the transformed halogen atom in some experiments. As evidenced by 1H NMR analysis of the modified products, the halogen end group can really be converted into the much more stable carbon-hydrogen structure. When Cu0 is not used, the conversion of the halogen end groups rises rapidly during the early stage and the increase rate slows down after about 8 h reaction. In view of the influence of reaction temperature on the modification, the conversion increases almost exponentially with temperature in the range of 80-100 °C, and the increase rate slows down at higher temperature. 1H NMR and SEC analyses prove that the modification reaction does not destroy the polymer backbone and the molecular weights remain almost the same as those of the unmodified samples. When Cu0 is introduced, the modification reaction proceeds much rapidly, the conversion of the halogen end groups rises almost linearly at the early stage and the nearly complete (>95%) dehalogenation of the polymeric chains is observed after only 12 h reaction. However, the molecular weights rise and the polydispersities become wider after the modification, which implies that the modification is accompanied with the couple termination of the polystyrene radicals besides chain transfer reaction. Furthermore, the couple termination can be restrained at some lower catalyst concentration. Indeed, the modified polymers show improved thermal stability, the initial weight loss temperatures is increased from 196 °C to 378 °C for the linear polystyrene and from 203 °C to 261 °C for the hyperbranched polystyrene. 相似文献
896.
The gold nanoprisms (GNPs) have exhibited special plasmonic properties for biomedical applications because of their unique shapes and dimensions. Based on their optical performance, the NIR dye IR780 not only enabled the GNPs-based nanosystem as SERRS nanoparticles for Raman-encoded molecular imaging, but also enhanced the plasmonic photothermal property by laser irradiation. Meanwhile, the GNPs/IR780-Lyp-1 by introduction of tumor-homing peptide segment LyP-1, which presents high affinity to p32 protein, demonstrated the increased enrichment in tumor region and enhanced photothermal therapy efficacy. 相似文献
897.
898.
Oxidative free radical reactions of enamino esters are described. Electrophilic carbon-centered radicals produced by the cerium(IV) ammonium nitrate (CAN) oxidation of β-dicarbonyl compounds undergo efficient addition to the C-C double bond of enamino esters. This CAN mediated free radical reaction between enamino esters and β-dicarbonyl compounds provides a novel method for the synthesis of highly substituted pyrroles. The direct CAN oxidation of β-enaminocinnamates gave the dimerization products effectively. 相似文献
899.
Yu H Chokhawala H Karpel R Yu H Wu B Zhang J Zhang Y Jia Q Chen X 《Journal of the American Chemical Society》2005,127(50):17618-17619
A multifunctional sialyltransferase has been cloned from Pasteurella multocida strain P-1059 and expressed in E. coli as a truncated C-terminal His6-tagged recombinant protein (tPm0188Ph). Biochemical studies indicate that the obtained protein is (1) an alpha2,3-sialyltransferase (main function), (2) an alpha2,6-sialyltransferase, (3) an alpha2,3-sialidase, and (4) an alpha2,3-trans-sialidase. The recombinant tPm0188Ph is a powerful tool in the synthesis of structurally diverse sialoside libraries due to its relaxed substrate specificity, high solubility, high expression level, and multifunctionality. 相似文献
900.
Seven new compounds, sodium aristolochate-VII (1), aristolactam-CIV (2), madolin-I (3), -J (4), -K (5), -L (6) and -M (7) together with 71 known compounds were isolated and characterized from the fresh root and stem of Aristolochia heterophylla Hemsl. Their structures were determined by spectral methods. Compound 8 was revised as aromadendrane-4beta, 10beta-diol by spectral data and single-crystal X-ray analysis. 相似文献