Journal of Theoretical Probability - Let G be a finite group. The commuting chain on G moves from an element x to y by selecting y uniformly amongst those which commute with x. The t-step... 相似文献
An efficient and rapid synthesis of the CDEF ring system of lactonamycinone is reported via a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disilyloxybenzocyclobutene and the appropriate γ-alkylidenebutenolide. The feasibility and the total chemoselectivity of the [4 + 2] cycloaddition for the construction of a spirolactone moiety via an intramolecular approach (IMDA) using both partners is also described demonstrating the versatility of the γ-alkylidenebutenolide building block. 相似文献
The aim of this research is to study the normalized fluorescence spectra (intensity variations and area under the fluorescence
signal), relative quantum yield, extinction coefficient and intracellular properties of normal and malignant human bone cells.
Using Laser-Induced Fluorescence Spectroscopy (LIFS) upon excitation of 405 nm, the comparison of emission spectra of bone
cells revealed that fluorescence intensity and the area under the spectra of malignant bone cells was less than that of normal.
In addition, the area ratio and shape factor were changed. We obtained two emission bands in spectra of normal cells centered
at about 486 and 575 nm and for malignant cells about 482 and 586 nm respectively, which are most likely attributed to NADH
and riboflavins. Using fluorescein sodium emission spectrum, the relative quantum yield of bone cells is numerically determined. 相似文献
Investigation on the leaves of Melicope bonwickii (F.Muell.) T.Hartley (Rutaceae) afforded a new 7-(2'-hydroxy-3'-chloroprenyloxy)-4-methoxyfuroquinoline (1) together with the known 7-(2',3'-epoxyprenyloxy)-4-methoxyfuroquinoline (2), evellerine (3) kokusaginine (4) and an amide aurantiamide acetate (5). Compounds 1 and 2 showed significant activity against cervical cell lines (Hela). 相似文献
A new coumarin, 8,4'-dihydroxy-3',4'-dihydrocapnolactone-2',3'-diol (1) and two known triterpenes, 5(6)-gluten-3-one (2) and 5(6)-gluten-3alpha-ol (3) were isolated from the leaves of Micromelum minutum (Rutaceae) collected from Sepilok, Sabah, Malaysia and their structures were characterized by spectroscopic methods. 相似文献
Homocystine was for the first time, chemically linked to a highly cross-linked agarose support (Novarose) to be employed as a chelating adsorbent for preconcentration and AAS determination of nickel in table salt and baking soda. Nickel is quantitatively adsorbed on a small column packed with 0.25 ml of the adsorbent, in a pH range of 5.5–6.5 and simply eluted with 5 ml of a 1 mol l−1 hydrochloric acid solution.
A factorial design was used for optimization of the effects of five different variables on the recovery of nickel. The results indicated that the factors of flow rate and column length, and the interactions between pH and sample volume are significant.
In the optimized conditions, the column could tolerate salt concentrations up to 0.5 mol l−1 and sample volumes beyond 500 ml. Matrix ions of Mg2+ and Ca2+, with a concentration of 200 mg l−1, and potentially interfering ions of Cd2+, Cu2+, Zn2+ and Mn2+, with a concentration of 10 mg l−1, did not have significant effect on the analyte's signal. Preconcentration factors up to 100 and a detection limit of 0.49 μg l−1, corresponding to an enrichment volume of 500 ml, were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked nickel in table salt and baking soda solutions resulted in quantitative recoveries. Direct ETAAS determination of nickel in the same samples was not possible because of a high background observed. 相似文献
Several molecularly imprinted polymers (MIPs) were prepared in the present work, and their binding properties were evaluated in comparison with a nonimprinted polymer (NIP). An optimized MIP was selected and applied for selective extraction and analysis of haloperidol in rabbit brain tissue. A molecularly imprinted solid-phase extraction (MISPE) method was developed for cleanup and preconcentration of haloperidol in brain samples before HPLC-UV analysis. Selectivity of the MISPE procedure was investigated using haloperidol and some structurally different drugs with similar polarity that could exist simultaneously in brain tissue. The extraction and analytical process was calibrated in the range of 0.05–10 ppm. The recovery of haloperidol in this MISPE process was calculated between 79.9 and 90.4 %. The limit of detection (LOD) and the limit of quantification (LOQ) of the assay were 0.008 and 0.05 ppm, respectively. Intraday precision and interday precision values for haloperidol analysis were less than 5.86 and 7.63 %, respectively. The MISPE method could effectively extract and concentrate haloperidol from brain tissue in the presence of clozapine and imipramine. Finally, the imprinted polymer was successfully applied for the determination of haloperidol in a real rabbit brain sample after administration of a toxic dose. Therefore, the proposed MISPE method could be applied in the extraction and preconcentration before HPLC-UV analysis of haloperidol in rabbit brain tissue. 相似文献
A Schiff base ligand was synthesized by the condensation of salicylaldehyde with l-tyrosine. Interaction of this ligand with Mn(II)-exchanged zeolite Y leads to encapsulation of the ligand within the zeolite and complexation of the metal. The encapsulated complex has been characterized by spectroscopic studies and chemical analyses. This material serves as a catalyst for the oxidation of cyclohexene to cyclohexene epoxide and 2-cyclohexene-1-ol using H2O2 as oxidant. The reaction conditions have been optimized for solvent, temperature and amount of oxidant and catalyst. The catalyst shows high activity and selectivity toward production of cyclohexene epoxide in acetonitrile at 60 °C with [H2O2]/[C6H10] = 2.5 molar ratio. Comparison of the encapsulated catalyst with the corresponding homogeneous catalyst showed that the heterogeneous catalyst had higher activity and selectivity than the homogeneous catalyst. 相似文献