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991.
992.
钨—镍—铁系重合金中粘结相的定量测定 总被引:3,自引:0,他引:3
通过对93W-Ni-Fe-Co(Mn)合金中粘结相和钨颗粒化学及电化学性质的研究,提出了一种定量提取W-Ni-Fe系重合金中粘结相的电解液,建立了定量测定其粘结相和钨颗粒组成及含量的方法。 相似文献
993.
Qi Wei Li Liu Zuo-Ren Nie Hui-Qiao Chen Jing-Xia Zou 《Journal of Sol-Gel Science and Technology》2007,44(2):105-110
Fluorocarbon groups were used to modify the pore channels of ethane-bridged periodic mesoporous organosilica by the co-condensation
of 1,2-Bis(triethoxysilyl)ethane (BTESE) and trifluoropropyltrimethoxysilane (TFPTMS) in the presence of Poly(ethylene glycol)-B-Poly(propylene
glycol)-B-Poly(ethylene glycol) (P123) surfactants under acidic conditions. The functionalized materials were investigated
in detail by means of XRD, TEM, FT-IR, solid-state NMR, and N2 adsorption. The effect of fluorocarbon groups concentration on the mesoscopic order and pore structure of the functionalized
materials was also studied. The results show that bridging groups in the framework do not cleave and fluorocarbon groups are
attached covalently to the pore wall of periodic mesoporous organosilica after functionalization. The samples functionalized
with 20% TFPTMS remain desired mesoporous architecture, with a narrow pore size distribution centered at 4.1 nm, a large surface
of 834 m2/g and a pore volume of 0.91 cm3g−1, without pronounced change compared to the pure periodic mesoporous organosilica. Unfortunately the functionalized materials
become structurally disordered with increasing amount of fluorocarbon groups. 相似文献
994.
995.
低剂量氯化钐对大鼠血清激素水平的影响 总被引:13,自引:3,他引:13
应用放射免疫法测定了经腹腔注射、灌胃入尾静脉注射等3种不同方式,隔日给预寺鼠低剂量氯化钐0.05mg/kg,一个月后,测试血清中生长激素,甲状腺素T3、T3及胰岛素水平。结果显示各实验组动物血清中生长激素、胰岛素水平均明显增高,甲状腺素T4及腹腔注射增高,其余两组无明显变化。 相似文献
996.
The use of a piezoelectric quartz crystal detector is proposed for monitoring the course of a titration reaction by observation of the frequency shift of the oscillating crystal. Satisfactory titrations can often be obtained using the acid-base technique, which is much more sensitive than the classical conductimetric titration and oscillometric titrration, with a lowest titratable concentration that is much lower but which can still be applied in the presence of a large amount of unreacting electrolyte. 相似文献
997.
Jin Huang Guang-xun Li Gao-feng Yang Ding-qiang Fu Xiao-kang Nie Xin Cui Jin-zhong Zhao Zhuo Tang 《Chemical science》2021,12(13):4789
N-Substituted tetrahydroquinoxalines (37 examples) were step-economically obtained in good yield (<97%) and ee (<99%) with readily available substrates. The reaction proceeds through an interesting regioselective Heyns rearrangement/enantioselective transfer hydrogenation in one pot. The substrate scope and the reaction mechanism were systematically investigated. N-Substituted tetrahydroquinoxalines were step-economically obtained in good yield and ee with readily available substrates. 相似文献
998.
Nie AiHua Xiao JunHai Wang LiLi Liao GuoChao Liu HongYing Ren Shen Li Song 《中国科学B辑(英文版)》2007,50(3):405-417
By choosing neuroimmunophilin FKBP12 as a therapeutical target, we have attempted to discover a new structural drug for treating
neurodegenerative disease. This drug should possess neurotrophic activity and not affect the immune system. Based on the crystal
structure of FKBP12, FK506 and Calcineurin complex, a series of small organic molecules were designed. These molecules were
to have the ability of binding to FKBP12 in a virtual screening. By using a solution parallel synthetic method, these compounds
were synthesized. The neuroprotective and neuroregenerative activities of these compounds were evaluated by binding assays,
PC12 cells survival and neurite outgrowth model, chick dorsal root ganglion cultures (DRG) and 6-OHDA lesioned mice sympathetic
nerve endings model. The evaluation results of these compounds showed that compound N308 has great promise as a candidate
for a neuroprotective and neuroregenerative agent.
Supported by the National Basic Research Program of China (Grant No. G1998051107) and Hi-tech Research and Development Program
of China (Grant No. 2002AA233051) 相似文献
999.
The fabrication, structure, electrochemical properties, and electrocatalytic properties of a manganese(III)-substituted Dawson-type phosphopolyoxotungstate, alpha 2-K7P2W17O61(Mn3+.OH2).12H2O (P2W17Mn), entrapped in polypyrrole (PPy) film have been studied. The hybrid film was prepared by potentiostatic polymerization from aqueous solution containing 20 mM pyrrole (Py) and 2 mM P2W17Mn on a pyrolytic graphite (PG) surface. Chronoamperometry, Raman spectroscopy, UV-visible absorption spectroscopy, and cyclic voltammetry were used to monitor and characterize the growth, structure, and properties of the film. The chronoamperometric curve shows that P2W17Mn can catalyze the electrochemical polymerization of Py. The Raman spectrum suggests that the doped P2W17Mn has little effect on the structure of PPy film. The P2W17Mn/PPy film exhibits good voltammetric response in both the acidic aqueous and acetonitrile solutions. At pH 1.0, the molar ratio of pyrrole to P2W17Mn7- in the hybrid film is 21.1:1, quite close to the expected ratio of 21.2:1 for a PPy film with a +0.33 oxidation level per pyrrole moiety and doped with an anion with a charge of 7. The influence of solution pH on P2W17Mn7- in the film is much smaller than that in the aqueous solution. During the potential scanning in 0.1 M LiClO4 acetonitrile solution, P2W17Mn7- was slowly released from the hybrid film and electrolyte ions (Li+ and ClO4-) were inserted into the film. This was identified by cyclic voltammetry and UV-visible spectroscopy. Additionally, the hybrid film can effectively catalyze the reduction of hydrogen peroxide and nitrite. 相似文献
1000.
A piezoelectric detector is used to monitor titration reactions involving complex formation or precipitation. Analytes at concentrations down to 10?4 mol 1?1 can be determined. The frequency shift in the compleximetric titrations is affected by the composition of the solution, the buffer and competing ligands present in the solution. Factors influencing the frequency shift in the precipitation titration are also investigated. 相似文献