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191.
微分倒数示波计时电位法的研究—定量测试及滴定分析 总被引:3,自引:0,他引:3
首次利用微分倒数示波图定量测试微量金属离子并滴定分析药物,结果满意。 相似文献
192.
Estimation of the aqueous solubility of organic molecules by the group contribution approach 总被引:1,自引:0,他引:1
Several group contribution methods to estimate the aqueous solubility of organic molecules are proposed and evaluated for their ability to predict the water solubility of new molecules. The learning set consisted of 1168 organic compounds with experimental data taken from the literature after critical evaluation. The best method, based on a new fragment atom scheme, leads to a squared correlation coefficient of 0.95 and an average absolute calculation error of 0.50 log unit, which is superior to other group contribution methods currently available. One of the advantages of this model is that it has upper and lower limits so that the predicted solubilities cannot be unrealistily high or low. 相似文献
193.
Two new coordination polymers of PbII complexes with bridging 4,4′‐[(1E)‐ethane‐1,2‐diyl]bis[pyridine] (ebp), thiocyanato, and acetato ligands, [Pb(μ‐SCN)2(μ‐ebp)1.5]n ( 1 ) and {[Pb(μ‐OAc)(μ‐ebp)](ClO4)}n ( 2 ), were synthesized and characterized by elemental analysis, FT‐IR, 1H‐ and 13C‐NMR, thermal analysis, and single‐crystal X‐ray diffraction. In 1 , the Pb2+ ions are doubly bridged by both the ebp and the SCN− ligands into a two‐dimensional polymeric network. The seven‐coordinate geometry around the Pb2+ ion in 1 is a distorted monocapped trigonal prism, in which the Pb2+ ions have a less‐common holodirected geometry. In 2 , the Pb2+ ions are bridged by AcO− ligands forming linear chains, which are also further bridged by the neutral ebp ligands into a two‐dimensional polymeric framework. The Pb2+ ions have a five‐coordinate geometry with two N‐atoms from two ebp ligands and three O‐atoms of AcO−. Although ClO acts as a counter‐ion, it also makes weak interactions with the Pb2+ center. The arrangement of the ligands in 2 exhibits hemidirected geometry, and the coordination gap around the Pb2+ ion is possibly occupied by a configurationally active lone pair of electrons. 相似文献
194.
Insulating tubular BN sheathing on semiconducting nanowires 总被引:1,自引:0,他引:1
Zhu YC Bando Y Xue DF Xu FF Golberg D 《Journal of the American Chemical Society》2003,125(47):14226-14227
An effective method was developed for generation of insulating tubular boron nitride (BN)-sheathed nanostructures. ZnS nanowires and multilayered Si-SiO2 nanowires were successfully sheathed with insulating tubular BN-forming nanocables. Both the semiconductor nanowire cores and the BN sheaths are crystalline with well-uniform morphologies. 相似文献
195.
A series of carbon-covered titania (CCT) were prepared via pyrolysis of sucrose highly dispersed on titania surface in flowing
N2. The samples were characterized by XRD, BET, DTA-TG, UV—Vis, and their photocatalytic properties were evaluated with two
model pollutants, methylene blue (MB) and rhodamine B (RB), at room temperature. The effect of carbon content on photocatalytic
activity of the C/TiO2 composite was investigated. It was found that the effect of carbon content is different for different pollutants or different
light sources. For three tested samples, under UV illumination CCT01 has the highest activity for MB photocatalytic degradation,
while in the case of RB, CCT02 is the most active photocatalyst. Under visible light illumination, CCT005 has the highest
activity for both MB and RB photocatalytic degradation.
Translated from Chinese Journal of Catalysis, 2006, 27(1): (in Chinese) 相似文献
196.
二维卷积在动力学分析中的应用 总被引:2,自引:0,他引:2
本文用计算机模拟和二维卷积研究了稀土与间乙酰基偶氮氯膦的显色反应,选择不同的模型参数可描述这类反应的细节,二维卷积则增强对叠合二维谱的分辨。 相似文献
197.
[reaction: see text] A catalyst for enolate formation was designed that incorporates an amine base along with a thiourea to bind to the oxygen atom of the substrate and enolate through hydrogen bonding. A computational model of the transition state was developed in which the thiourea (modeled initially as a urea) and amine were separate molecules. This model and models incorporating one or two methanol molecules in place of the urea showed an out-of-plane hydrogen bond, apparently to the carbonyl pi-bond, in addition to an in-plane hydrogen bond to an unshared electron pair. In contrast, optimized complexes of the ketone and the fully formed enolate showed only in-plane hydrogen bonding. The transition state model with the urea and amine was used to define a database search with the computer program CAVEAT to identify structures suitable for linking the amine and urea/thiourea moieties in the transition state. On the basis of a group of structures identified from this search, a flexible but conformationally biased linker was designed to connect the two catalytic moieties. The molecule having the amine and thiourea moieties connected by this linker was synthesized and was shown to catalyze proton exchange between methanol and deuterated acetone. The catalyst was about 5-fold more efficient than the amine and thiourea as separate molecules and relative to a similar but less conformationally biased catalyst. 相似文献
198.
QijianZhang DehuaHe QimingZhu 《天然气化学杂志》2003,12(2):81-89
The direct conversion of methane to methanol has attracted a great deal of attention for nearly a century since it was first found possible in 1902, and it is still a challenging task. This review article describes recent advancements in the direct partial oxidation of methane to methanol. The history of direct oxidation of methane and the difficulties encountered in the partial oxidation of methane to methanol are briefly summarized. Recently reported developments in gas-phase homogeneous oxidation, heterogeneous catalytic oxidation and liquid phase homogeneous catalytic oxidation of methane axe reviewed. 相似文献
199.
Yiyi Weng Xingxing Ding Joo C. A. Oliveira Xiaobin Xu Nikolaos Kaplaneris Meijie Zhu Hantao Chen Zhuo Chen Lutz Ackermann 《Chemical science》2020,11(34):9290
There is a strong demand for novel native peptide motifs for post-synthetic modifications of peptides without pre-installation and subsequent removal of directing groups. Herein, we report an efficient method for peptide late-stage C(sp3)–H arylations assisted by the unmodified side chain of asparagine (Asn) without any exogenous directing group. Thereby, site-selective arylations of C(sp3)–H bonds at the N-terminus of di-, tri-, and tetrapeptides have been achieved. Likewise, we have constructed a key building block for accessing agouti-related protein (AGRP) active loop analogues in a concise manner.An efficient method for peptide late-stage C(sp3)-H arylations assisted by unmodified side chain of asparagine (Asn) without any exogenous directing group has been reported. 相似文献
200.
Annals of the Institute of Statistical Mathematics - The research is about a systematic investigation on the following issues. First, we construct different outcome regression-based estimators for... 相似文献