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121.
Ning Liu Shunzhong Luo Yuanyou Yang Taiming Zhang Jiannan Jin Jiali Liao 《Journal of Radioanalytical and Nuclear Chemistry》2002,252(1):187-191
The biosorption of radionuclide 241Am from solution by Saccharomyces cerevisiae (S. cerevisiae), and the effects of experimental conditions on the adsorption were investigated. The preliminary results showed thatS. cerevisiae is a very efficient biosorbent. An average of more than 99% of the total 241Am could be removed by S. cerevisiae of 2.1 g/l (dry weight) from 241Am solutions of 17.54–4386.0 mg/l (2.22 MBq/l–555 MBq/l) with adsorption capacities of 7.45–1880.0 mg/g biomass (dry weight) (0.94 MBq/g–237.9 MBq/g). The adsorption equilibrium was achieved within 1 hour and the optimum pH ranged 1–3. No significant differences on 241Am adsorption were observed at 10–45 °C, or in solutions containing Au3+ or Ag+, even 2000 times above 241Am concentration. The relationship between concentrations and adsorption capacities of 241Am indicated the biosorption process should be described by the Freundlich adsorption isotherm. 相似文献
122.
采用密度泛函理论(DFT), 在B3LYP/6-311++G(d,p)基组上计算得到了21种N8H8链状异构体, 并研究了这些异构体间可能的互变异构情况. 为了得到更为精确的能量信息, 计算了QCISD(T)/6-311G(d,p)基组水平上各物质的能量. 所得的21种异构体分为4类(4种类型链状化合物): A为直链, B有一个支链, C有2个支链, D有3个支链; D类只有一种, A类稳定构型2种, B类稳定构型12种, C类稳定构型6种; 相对稳定的分别为: B2-1构型, B2-3构型和C23-2构型. 我们研究发现N8H8链状异构体中含有明显N=N双键特征有利于化合物稳定性的提高. 相似文献
123.
ZrO2-TiO2-CeO2的制备及其在NH3选择性催化还原NO中的应用 总被引:1,自引:0,他引:1
采用共沉淀法制备了载体材料TiO2、ZrO2-TiO2及ZrO2-TiO2-CeO2, 并利用X射线衍射(XRD)实验、比表面积测定(BET)、程序升温脱附(NH3-TPD)、储氧性能测定(OSC)及程序升温还原(H2-TPR)等方法对三种载体材料进行了表征. 结果表明, ZrO2-TiO2-CeO2具有较多的表面强酸位, 并具有一定的储氧性能和较强的氧化还原性能. 以三种材料为载体, 制备了质量分数分别为1%、9%的V2O5、WO3的整体式催化剂. 研究了三种催化剂在富氧条件下用NH3选择性催化还原NO的催化性能. 结果表明, 以ZrO2-TiO2-CeO2为载体的催化剂在反应空速为10000 h-1, 275 ℃时, NO的转化率接近100%, 具有最好的催化活性,并有良好的应用前景。 相似文献
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125.
S. C. Cheng W. Feng I. I. Pashikin L. H. Yuan H. C. Deng Y. Zhou 《Radiation Physics and Chemistry》2002,63(3-6):517-519
Temperature-sensitive poly (N-vinylcaprolactam) both in water-soluble state and in gel was prepared by γ-radiation polymerization. The effects of radiation dose, radiation dose rate and monomer concentration on polymerization and the low critical solution temperature characteristics of the polymer were studied. The results show that the polymer prepared within certain radiation dose (beyond 2 kGy) and dose rate range (2–14 Gy/min) has good temperature sensitivity and uniformity. 相似文献
126.
Qing Z Wen-Chen Z Xiao-Xuan W Yang M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):769-772
From the high-order perturbation formulas of EPR parameters (zero-field splitting D, g factors gparallel, gperpendicular and hyperfine structure constants Aparallel, Aperpendicular) based on the two spin-orbit coupling parameter model for 3d3 ions in trigonal symmetry, the EPR parameters of Cr3+ and V2+ ions in HfS2 crystals are calculated. From the calculations, it is found that the local trigonal distortion angle theta of impurity center in HfS2:Cr3+ is smaller than that in HfS2:V2+. The dominant cause of the small zero-field splitting |D| and g-anisotropy |Deltag|=|gparallel-gperpendicular| in HfS2:Cr3+ (compound to HfS2:V2+) is due to the small local trigonal distortion angle theta rather than to the small impurity-ligand distance R in HfS2:Cr3+. 相似文献
127.
Shao-Yi W Wen-Chen Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(14):3179-3183
The electron paramagnetic resonance (EPR) g factors g(parallel), g(perpendicular) and hyperfine structure parameters A(parallel), A(perpendicular) of the tetragonal Er3+ centers in zircon-type compounds YXO4 (X = As, P, V), ScVO4 and RSiO4 (R = Zr, Hf, Th) are calculated from the perturbation formulas of EPR parameters for 4f11 ion in tetragonal symmetry. In these formulas, the second-order perturbation contributions are included in addition to the first-order perturbation contributions considered in the previous papers. The crystal-field parameters used in the calculations are obtained by analyzing the optical spectral data from the superposition model. Although the superposition model intrinsic parameters An(R0) used in this paper for Er3+ in various zircon-type compounds are not as scattered as those in the previous paper, the calculated results of both the optical spectra and EPR parameters show better agreement than those in the previous paper with the observed values, suggesting that the above calculation method and parameters are more reasonable. The contributions of the second-order perturbation terms to EPR parameters are also discussed. 相似文献
128.
Wen-Chen Z Shao-Yi W Jian Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(4):751-754
The EPR g factors g(parallel), g(perpendicular) and zero-field splitting D suggested to be caused by a donor-acceptor nearest-neighbour pair defect [Ti(Ga)(2+)-Sp] in GaP:Ti(2+) co-doped with sulphur are calculated from the high-order perturbation formulas based on a two spin-orbit coupling parameter model for the EPR parameters of 3d(2) ion in trigonal symmetry. The calculated results are close to the observed values. The suggestion of [Ti(Ga)(2+)-Sp] pair defect in GaP:Ti co-doped with sulphur is also confirmed from this calculation. 相似文献
129.
130.
A new biodegradable polymer system, poly(p-dioxanone) (PPDO)/poly(ethylene glycol) (PEG) blend was prepared by a solvent casting method using chloroform as a co-solvent. The PPDO/PEG blends have different weight ratios of 95/5, 90/10, 80/20 and 70/30. Crystallization of homopolymers and blends were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). When 5% of PEG was blended, the crystallization exothermal peaks (Tc) of PPDO increased sharply and the crystallization exothermal peaks (Tc) of PEG decreased slightly compared with the homopolymers. The crystallization rates of both components increased, and caused greater relative crystallization degree (Xt%). But when the content of PEG was more than 5%, the crystalline behaviors of blends had no more significant changes accordingly. The melting points of each sample varied little over the entire composition range in this study. The nonisothermal crystallization of PPDO homopolymer and blend (PPDO/PEG = 70/30) were also studied by DSC. The crystallization began at a higher temperature when the cooling rates were slower. The nonisothermal crystallization kinetics of blends was analyzed by Ozawa equation. The results showed that the Ozawa equation failed to describe the whole crystallization of the blend, but Mo equation could depict the nonisothermal crystallization perfectly. 相似文献