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991.
An interesting sequential Sonogashira coupling/alkynyl imine-allenyl imine isomerization/aza-Diels-Alder/elimination-aromatization reaction, providing a facile synthesis of substituted 2-azaanthracenes from 1,6-diynes and imidoyl chlorides, is reported. The easy procedure accessing the products efficiently from readily available starting materials may imply a potential synthetic application. 相似文献
992.
Zeng J Wang W Deng P Feng W Zhou J Yang Y Yuan L Yamato K Gong B 《Organic letters》2011,13(15):3798-3801
Hydrogen-bonded zippers bearing terminal alkene groups were treated with Grubbs' catalyst, leading to covalently cross-linked zippers without violating H-bonding sequence specificity. The yield of a cross-linked zipper depended on the stability of its H-bonded precursor, with a weakly associating pair giving reasonable yields only at high concentrations while strongly associating pairs showed nearly quantitative yields. The integration of thermodynamic (H-bonding) and kinetic (irreversible C═C bond formation) processes suggests the possibility of developing many different covalent association units for constructing molecular structures based on a self-assembling way. 相似文献
993.
An efficient and straightforward strategy for the synthesis of N-(2-haloinden-1-yl)arenesulfonamides from propargylic alcohols and sulfonamides is described. Allenesulfonamide is postulated to be the key intermediate for this tandem transformation. 相似文献
994.
Inverted carbenoid species, generated from attack of phosphines at the α(δ')-carbon of hex-2-en-4-ynedioic acid dialkyl esters, react with aldehydes to give γ-lactones possessing an α-phosphorus ylide moiety. 相似文献
995.
Wu Y Jiang F Chen L Zheng J Deng Z Tao Q Zhang J Han L Wei X Yu A Zhang H 《Analytical and bioanalytical chemistry》2011,400(7):2141-2147
A new micellar electrokinetic chromatography (MEKC) method using beta-cyclodextrins (β-CDs) and 1-butyl-3-methylimidazolium hexafluorophosphates (ionic liquids) as additives was successfully developed for determination of para-, meta-, and ortho-phenylenediamines isomers (p-P, m-P, and o-P) in hair dyes. To improve the sensitivity of the MEKC-UV, a simple and cheap flow injection (FI) technique using a micro-column packed with coal cinders (the by-products from combustion in a boiler) as solid-phase extractant was also investigated. In the presence of 20 mmol L(-1) phosphates at pH 5.5, addition of 12 mmol L(-1) ionic liquids and 8 mmol L(-1) β-CDs greatly improved the separation efficiency. The three analytes could be quantitatively adsorbed by coal cinders, and desorbed readily with 0.15 mL of 0.01 mol L(-1) NaOH. Under the optimum conditions, an enrichment factor (EF) of 33.3 was obtained, and determination limits of p-P, m-P, and o-P were 1.97?×?10(-7), 0.99?×?10(-7), and 0.61?×?10(-7) mol L(-1), respectively. The adsorption capacities of the coal cinders micro-column for p-P, m-P, and o-P were all 1.20 mg g(-1). The presented procedure was successfully applied to the determination of p-P, m-P, and o-P in hair dyes with satisfactory results. 相似文献
996.
Deng B Wang Z Song J Xiao Y Chen D Huang J 《Analytical and bioanalytical chemistry》2011,401(7):2143-2152
The doxorubicin (DOX) uptake in single human leukemia K562 cells with changes in both drug dosage and exposure period was
studied using capillary electrophoresis (CE) coupled with laser-induced fluorescence (LIF) detection. The cells were treated
with DOX at different concentrations (1, 3, 10, 20, 30, and 50 μM) and for different exposure times (1, 3, 5, 24, and 48 h).
At least 20 cells were analyzed for each DOX-treated cell population. A marked heterogeneity in DOX uptake among single cells
was observed, because the relative standard deviation of the uptake of DOX by single cells ranged from 24.0% to 61.1% within
each cell population. The cell-to-cell heterogeneity in DOX uptake first decreased and then became constant with increasing
drug concentration, but it did not exhibit regular variation with increasing exposure time. The mean DOX uptake was a linear
function of drug concentration (r ≥ 0.9667). In terms of the correlation with exposure time, the mean DOX uptake reached its maximum at 3 h for the cell populations
treated with 1–10 μM DOX, while it kept increasing during 48 h exposure of cell populations to 20–50 μM DOX. Because it eliminates
DOX fluorescence quenching and sample loss, the CE-LIF method directly detects the true DOX uptake by single cells, and thus
presents accurate information on both the cell-to-cell heterogeneity in DOX uptake and the patterns of DOX uptake in K562
cells as functions of drug concentration and exposure time. 相似文献
997.
Xuezhe Zhao Shengwei Deng Yongmin Huang Honglai Liu Ying Hu 《Frontiers of Chemistry in China》2011,6(3):159-163
The wrinkling of phase-separated binary polymer blend film was studied through combining the Monte Carlo (MC) simulation for
morphologies with the lattice spring model (LSM) for mechanical properties. The information of morphology and structure obtained
by use of MC simulation is input to the LSM composed of a three-dimensional network of springs, which allows us to determine
the wrinkling and the mechanical properties of polymer blend film, such as strain, stress, and Young’s modulus. The simulated
results show that the wrinkling of phase-separated binary polymer blend film is related not only to the structure of morphology,
but also to the disparity in elastic moduli between polymers of blend. Our simulation results provide fundamental insight
into the relationship between morphology, wrinkling, and mechanical properties for phase-separated polymer blend films and
can yield guidelines for formulating blends with the desired mechanical behavior. The wrinkling results also reveal that the
stretching of the phase-separated film can form the micro-template, which has a wide application prospect. 相似文献
998.
Dianliang Deng 《Journal of Mathematical Analysis and Applications》2011,376(1):136-153
Let X,X1,X2,… be a sequence of nondegenerate i.i.d. random variables with zero means. Set Sn=X1+?+Xn and . In the present paper we examine the precise asymptotic behavior for the general deviation probabilities of self-normalized sums, Sn/Wn. For positive functions g(x), ?(x), α(x) and κ(x), we obtain the precise asymptotics for the following deviation probabilities of self-normalized sums:
999.
A geometric construction of quantum Schur algebras was given by Beilinson, Lusztig and MacPherson in terms of pairs of flags in a vector space. By viewing such pairs of flags as representations of a poset, we give a recursive formula for the structure constants of quantum Schur algebras which is related to certain Hall polynomials. As an application, we provide a direct proof of the fundamental multiplication formulas which play a key role in the Beilinson-Lusztig-MacPherson realization of quantum gln. In the appendix we show how to groupoidify quantum Schur algebras in the sense of Baez, Hoffnung and Walker. 相似文献
1000.
The wave propagation in the piezoelectric bend rods with arbitrary curvature is studied in this paper. Basic three-dimensional equations in an orthogonal curvilinear coordinate system (r, θ, s) are established. The Bessel functions in radial co-ordinate and triangle series in the angular co-ordinate are used to describe the displacements and electrical potential. Characteristics of dispersion, distributions of displacements and electrical potential over the cross section are calculated, respectively. In the numerical examples, the effects of the ratio of the two ellipse axes on the dispersion relations of the first three modes are observed. The characteristics of the distribution of displacements and electric potential in the cross section, along the radial and s direction are investigated. 相似文献