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51.
Reactions of copper(I) halides with racemic 2,2′-bis(diphenylphosphano)-1,1′-binaphthyl (rac-binap) in 1:1 molar ratio afforded mononuclear complexes of the type [CuX(rac-binap)] (X = Cl, Br, I) which, on further treatment with 1 equiv. of pyridine-2-thione (py2SH), pyrimidine-2-thione (pymtH) or 4,6-dimethyl-pyrimidine-2-thione (dmpymtH) gave rise to the formation of mixed-ligand complexes of the formula [CuX(rac-binap)(thione)]. The molecular structures of [CuBr(rac-binap)(py2SH)] · 2CH2Cl2, [CuBr(rac-binap)(py2SH)] · CH2Cl2 and [CuBr(rac-binap)(dmpymtH)] · CH2Cl2 have been established by single-crystal X-ray diffraction. Each of the complexes features a distorted tetrahedral copper(I) center with the phosphane acting in a chelating fashion. The complexes are strongly luminescent in the solid state at ambient temperature. Unusually, the [CuBr(rac-binap)(py2SH)] · 2CH2Cl2 molecules crystallise in a chiral space group with independent S- and R-enantiomers in the asymmetric unit. 相似文献
52.
53.
Raufaste C Dollet B Cox S Jiang Y Graner F 《The European physical journal. E, Soft matter》2007,23(2):217-228
We study the two-dimensional flow of foams around a
circular obstacle within a long channel. In experiments, we
confine the foam between liquid and glass surfaces. In
simulations, we use a deterministic software, the Surface
Evolver, for bubble details and a stochastic one, the extended
Potts model, for statistics. We adopt a coherent definition of
liquid fraction for all studied systems. We vary it in both
experiments and simulations, and determine the yield drag of the
foam, that is, the force exerted on the obstacle by the foam
flowing at very low velocity. We find that the yield drag is
linear over a large range of the ratio of obstacle to bubble
size, and is independent of the channel width over a large range.
Decreasing the liquid fraction, however, strongly increases the
yield drag; we discuss and interpret this dependence. 相似文献
54.
Lai C. Chan Brian G. Cox Ian C. Jones Simone Tomasi 《Journal of Physical Organic Chemistry》2011,24(9):751-763
A detailed kinetic analysis and computational study of an SNAr reaction between 2,5,6‐trifluoronicotinonitrile, 2 , and the ambident 3‐isopropoxy‐1H‐pyrazol‐5‐amine, 3 , is presented. The selectivity with respect to the reaction at the primary amino group of 2 , to give the desired product, 2,5‐difluoro‐6‐[(3‐isopropoxy‐1H‐pyrazol‐5‐yl)amino]nicotinonitrile, 1 , is strongly dependent upon reaction conditions. Reaction is found to proceed via both uncatalysed and base catalysed routes, and selectivity towards 1 is strongly enhanced in the presence of the base diazabicyclo[2,2,2]octane (DABCO). Computational studies in tetrahydrofuran solution at the B3LYP/6‐31G* level of theory have provided valuable insight into alternative kinetically indistinguishable reaction pathways. The results suggest that for reaction at the primary amino group, proton removal by DABCO accompanying amine addition allows avoidance of a high‐energy, zwitterionic Meisenheimer intermediate. Reactions at the alternative pyrazole nitrogen atoms are less sensitive to the presence of base because of stabilisation of the Meisenheimer zwitterions by intramolecular hydrogen bonding. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
55.
56.
D. Wayne Cooke Melvin Leon Michael A. Paciotti Peter F. Meier Stephen F. J. Cox Edward A. Davis Thomas L. Estle Bassam Hitti Roger L. Lichti Carolus Boekema John Lam Anny Morrobel-Sosa Jean Oostens 《Hyperfine Interactions》1994,86(1):699-704
A distinctive longitudinal magnetic field dependence of the muon polarization for anomalous muonium in polycrystalline semiconductor targets has been predicted. The polarization exhibits a cusp,i.e., a discontinuous jump in the slope from negative to positive. Measurements of the longitudinal polarization for polycrystalline silicon in fields up to 0.5 T, and temperatures 53 and 200 K have been made at LAMPF. A cusp in the field dependence indeed occurs at 0.345 T, in excellent agreement with the prediction. No cusp is observed at 200 K because Mu* has been thermally ionized. 相似文献
57.
This paper describes a technique to develop high-resolution three-dimensional (3D) images of microvasculature structures in curettage, hysterectomy or endometrial resection biopsies using parallel histological serial sections. Employing a labelled streptavidin-biotin-alkaline phosphatase (LSAB(+)) method and visualising by using DAB(+) with the primary antibody, mouse anti human Q-Bend-10, the images were directly digitised from a light microscope into the KS400 Universal Image Processing and Analysis software via a CCD colour camera; binary images of the structures were created and the binary images were exported into VoxBlast 3D rendering software to view still and rotating 3D images on a computer monitor. This in turn enabled hard copies of the full sequence to be printed. 相似文献
58.
In this work we investigated the relative merits of conventional single-photon confocal laser scanning fluorescence microscopy (CLSM) and two-photon laser scanning fluorescence microscopy (2p-LSM) for the study of mitochondria in living neurons. Dorsal root ganglion neurons were loaded with the mitochondrion-specific fluorescent dye JC-1, the ratio between red (J-aggregates) and green (monomer) fluorescence of which reflects mitochondrial membrane potential. Cells were illuminated at 488 nm for single-photon excitation or at 870 nm for two-photon excitation. In both modalities we found that mitochondria showed: (i) similar appearance; (ii) similar fluorescence ratio values over both whole cell bodies and individual mitochondria; and (iii) similar responses to mitochondrial uncoupler, which dropped the ratio values by 50%. However, 2p-LSM exhibited several advantages over CLSM: (i) better signal/noise ratio in the green emission channel; (ii) less phototoxicity upon repetitive scanning in the focal plane; and (iii) no significant loss of image quality upon repetitive scans in the z direction. We conclude that, while both techniques enable visualisation of individual mitochondria in living cells, 2p-LSM has significant advantages for physiological work requiring time-lapse experiments or four-dimensional reconstructions of mitochondria. 相似文献
59.
Let Z = {Z0, Z1, Z2,…} be a martingale, with difference sequence X0 = Z0, Xi = Zi ? Zi ? 1, i ≥ 1. The principal purpose of this paper is to prove that the best constant in the inequality λP(supi |Xi| ≥ λ) ≤ C supiE |Zi|, for λ > 0, is C = (log 2)?1. If Z is finite of length n, it is proved that the best constant is . The analogous best constant Cn(z) when Z0 ≡ z is also determined. For these finite cases, examples of martingales attaining equality are constructed. The results follow from an explicit determination of the quantity Gn(z, E) = supzP(maxi=1,…,n |Xi| ≥ 1), the supremum being taken over all martingales Z with Z0 ≡ z and E|Zn| = E. The expression for Gn(z,E) is derived by induction, using methods from the theory of moments. 相似文献
60.
The linear absorption of CO2 laser radiation in SF6, WF6, and UF6 has been measured by using optoacoustic detection techniques. Absolute absorption coefficients per Torr as low as 1 × 10?7 cm?1 Torr?1 in a 2-cm active path length could be measured by taking advantage of calibration measurements performed with SF6. 相似文献