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991.
A density functional theory and wave function theory investigation on the possibility of carbon-free phosphametallocenes [P3MP3]2? and arsenametallocenes [As3MAs3]2? (M=Ni, Pd, Pt) is presented in this work. Staggered singlet D3d [E3ME3]2? (E=P, As)-the smallest inorganic metallocenes possible to construct-proved to be the global minima of the heptaatomic systems and may be targeted in future experiments. Cyclo-P 3 ? and cyclo-As 3 ? turned out to possess similar aromaticity to cyclo-P 5 ? and cyclo-As 5 ? and may serve as effective ligands to sandwich a wide range of transition metals. The first vertical electron detachment energies of Cs [E3ME3]Li? monoanions with a staggered [E3ME3]2? sandwich core were predicted to be between 2.7 and 2.9 eV; the extent of stabilization by Li+ suggests that such materials be viable targets for experimental characterization. 相似文献
992.
Xue Wang Gang Sun ShiLing Sun ChunGuang Liu YongQing Qiu Qiang Fu 《中国科学:化学(英文版)》2010,53(8):1746-1753
Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculation were adopted to study the structures and properties of metal-free and magnesium tetrathieno[2,3-b]porphyrazine (TTPPzH2 and TTPPzMg) using B3LYP method with the 6–31G(d) basis set. A comparison of the geometrical structures, atomic charges, molecular orbitals, UV-vis spectra and infrared (IR) spectra among tetrathieno[2,3-b]porphyrazine (TTPPzH2), phthalocyanine (H2Pc) and porphyrazine (H2Pz) compounds was performed. The substituent effect of the thiophene heterocycle for electron-donating on the structures and properties of these compounds has been discussed. Compared with other atoms, the charge distribution of Cβ atoms adjacent to the sulfur atom is significantly influenced by the thiophene heterocycle substituents. The enlargement of the HOMO-LUMO gaps from H2Pc and MgPc to TTPPzH2 and TTPPzMg is at the origin of the observed blue shift of the Q band when moving from H2Pc to TTPPzH2 compounds. Special emphasis has been devoted to the strongest B bands for TTPPzH2 compounds which show red shift due to the large destabilization of the lower lying occupied orbitals compared with the corresponding B bands of H2Pc compounds. With the assistance of animated pictures produced on the basis of the normal coordinates, the significant peaks and vibration modes in the IR spectra of all the compounds were assigned and analyzed. 相似文献
993.
为了研究纳米碳酸钙和纳米添加剂在促进燃煤脱硫中的特性,在ZCS-1智能测硫仪中进行纳米碳酸钙脱硫实验研究。结果表明,在炉温900℃、钙硫比为2的条件下,脱硫效率高达90%;1 150℃时达到50%以上。三种纳米碳酸钙的脱硫效果明显好于普通碳酸钙。研究还表明,粒径越小,脱硫效果越好;不同煤种对脱硫效率有较大影响,主要和煤中硫分的含量和硫的分布形态有关;温度是决定脱硫效果的主要因素,900℃下效果最好,超过1 100℃后效果明显下降。SEM和BET分析结果表明,纳米碳酸钙促进脱硫主要是由于其较为丰富的孔隙结构。添加纳米Al2O3和纳米ZnO都能在一定程度上促进纳米碳酸钙脱硫。其中,纳米Al2O3的效果较好,1 150℃能使脱硫效率提高20%左右,达到62%以上。 相似文献
994.
Microchip-based systems have been developed rapidly due to their desirable advantages over conventional platforms. Higher level system integration and complex microdevices are emerging to satisfy the demand for high-throughput and large-scale applications. However, most of the devices need to be fabricated with complicated microvalves and micropumps, which, to some extent, limit the use of the novel technique. In this study, a simple microdevice was developed to perform chemotherapy resistance analysis in lung cancer cell line SPCA1. This device includes a PDMS chip for which a simple external small clip served as a microvalve to control the fluid flow so that the parallel control experiment could be carried out simultaneously, and a syringe pump, which supplied the cells with fresh medium mimicking the microenvironment in vivo. Cell culture, detection of drug resistance related protein P-glycoprotein (P-gp) and glutathione S-transferase-π (GST-π) and cell viability after VP-16 treatment on experimental (pretreated with corresponding inhibitors) and control groups were achieved. The results demonstrated that the cells could grow and spread well for at least 3 days. The expression of P-gp and GST-π was obviously downregulated by corresponding inhibitors. The percentage of apoptotic cells for P-gp inhibition group increased 2.9-fold compared with that of control group (23.7 ± 2.6 versus 8.1 ± 3.0%, p<0.05), while for GST-π inhibition, there was no obvious distinction between the experimental and control group. The simple microdevice is capable of integrating parallel operations involving cell culture and functional analysis, offering an easy and flexible platform for a stable long-term cell culture and comparison research. 相似文献
995.
A novel magnetic solid-phase extraction (MSPE) sorbent, magnetite/silica/poly (methacrylic acid–co-ethylene glycol dimethacrylate) (Fe3O4/SiO2/P(MAA-co-EGDMA)), was developed. This MSPE material was prepared by distillation–precipitation polymerization of MAA and EGDMA in the presence of Fe3O4/SiO2 microspheres with the surface containing abundant reactive double bonds. The resultant sorbent material was characterized by elemental analysis, electron microscopy, X-ray diffraction and Fourier-transformed infrared spectroscopy. In this work, eleven sulfonamides (SAs) were selected as model analytes to validate the extraction performance of this new MSPE sorbent. Noticeably, the extraction can be carried out quickly, the extraction time for the SAs onto Fe3O4/SiO2/P(MAA-co-EGDMA) sorbent can be clearly shortened to 0.5 min. The desorption solution of SAs was analyzed by LC–MS/MS, and the results showed that the recoveries of these compounds were in the range of 87.6–115.6%, with relative standard deviations ranging between 0.9% and 10.8%; the limit of detection were in the range of 0.5–49.5 ng/L. 相似文献
996.
997.
Gang Liu Tian‐Jun Wu Dr. Yuan‐Ping Ruan Prof. Pei‐Qiang Huang Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(19):5755-5768
The asymmetric total synthesis of natural azasugars (+)‐castanospermine, (+)‐7‐deoxy‐6‐epi‐castanospermine, and synthetic (+)‐1‐epi‐castanospermine has been accomplished in nine to ten steps from a common chiral building block (S)‐ 8 . The method features a powerful chiral relay strategy consisting of a highly diastereoselective vinylogous Mukaiyama‐type reaction with either chiral or achiral aldehydes (≥95 % de; de=diastereomeric excess) and a diastereodivergent reduction of tetramic acids, which allows formation of three continuous stereogenic centers with high diastereoselectivities. The method also provides a flexible access to structural arrays of 5‐(α‐hydroxyalkyl)tetramic acids, such as 17/34 , and 5‐(α‐hydroxyalkyl)‐4‐hydroxyl‐2‐pyrrolidinones, such as 18 and 25/35 a . The method constitutes the first realization of the challenging chiral synthons A and D and thus of the conceptually attractive retrosynthetic analysis shown in Scheme 1 in a highly enantioselective manner. 相似文献
998.
本文讨论了含割点$u$的连通图G,其中$G-u$含路、圈或$D_{n}$分支时图$G$的伴随多项式的最小实根的变化情况.得到一些新的序关系,这推广了文[10-13]中有关图的伴随多项式最小根的一些结果. 相似文献
999.
Feature extraction and selection from volatile compounds for analytical classification of Chinese red wines from different varieties 总被引:1,自引:0,他引:1
Jian Zhang Li Li Nianfa Gao Depei Wang Qiang Gao Shengping Jiang 《Analytica chimica acta》2010,662(2):137-271
This work was undertaken to evaluate whether it is possible to determine the variety of a Chinese wine on the basis of its volatile compounds, and to investigate if discrimination models could be developed with the experimental wines that could be used for the commercial ones. A headspace solid-phase microextraction gas chromatographic (HS-SPME-GC) procedure was used to determine the volatile compounds and a blind analysis based on Ac/Ais (peak area of volatile compound/peak area of internal standard) was carried out for statistical purposes. One way analysis of variance (ANOVA), principal component analysis (PCA) and stepwise linear discriminant analysis (SLDA) were used to process data and to develop discriminant models. Only 11 peaks enabled to differentiate and classify the experimental wines. SLDA allowed 100% recognition ability for three grape varieties, 100% prediction ability for Cabernet Sauvignon and Cabernet Gernischt wines, but only 92.31% for Merlot wines. A more valid and robust way was to use the PCA scores to do the discriminant analysis. When we performed SLDA this way, 100% recognition ability and 100% prediction ability were obtained. At last, 11 peaks which selected by SLDA from raw analysis set had been identified. When we demonstrated the models using commercial wines, the models showed 100% recognition ability for the wines collected directly from winery and without ageing, but only 65% for the others. Therefore, the varietal factor was currently discredited as a differentiating parameter for commercial wines in China. Nevertheless, this method could be applied as a screening tool and as a complement to other methods for grape base liquors which do not need ageing and blending procedures. 相似文献
1000.
Qiang Ma Chao Wang Hua Bai Wei Ma Xin Zhou Yiyang Dong Qing Zhang 《Chromatographia》2010,71(5-6):469-474
Liquid chromatographic methods based on reversed-phase, ion-pair and ion-exchange chromatography coupled with ultraviolet spectrometry and tandem mass spectrometry have been developed and compared for the determination of 8-hydroxyquinoline in cosmetic samples. The individual parameters of different techniques are systematically optimized. The reversed-phase chromatography using ultrasonic extraction, centrifugation and filtration prior to LC–UV and LC–MS–MS detection was selected to be the general analytical method for the routine analysis of 8-hydroxyquinoline in cosmetics due to its simplicity, column reproducibility and sensitivity. The procedure is rapid, simple and suitable for the quality control of cosmetic preparations. The application of this technique to the assay of commercial products is also presented. 相似文献