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931.
The spectral characteristics of erythropoietic cellular inclusions stained by May-Grunwald Giemsa (MGG) were determined by spectrally resolved imaging. Multipixel spectra were obtained from Cabot rings and Howell-Jolly (HJ) bodies, displaying a range of wavelengths of transmitted light. The spectral characteristics of these inclusions were compared with those of isolated DNA, his-tones (type II) and arginine-rich histones (type VI), all stained by MGG. Results of single-cell spectroscopy show that the spectra of Cabot rings and HJ bodies share spectral characteristics with the type II and type VI histones. However, no resemblance was found between Cabot rings and DNA spectra. The spectral analysis of hetero-chromatin displayed a spectral pattern with characteristics of both DNA and histones, while the euchromatin showed a major contribution of the DNA component. 相似文献
932.
Phosphorescence excitation and emission spectra, phosphorescence lifetimes, phosphorimetric analytical curves and limits of detection were determined at 77K in 10/90 v/v methanol/water solution for seven pyrimidine derivatives. The effect of pH on the phosphorescence intensity indicated an improvement of the sensitivity of the method in basic medium (pH reverse similar11). Low limits of detection, between 10(-5) and 10(-8)M, were obtained. The effect of sodium iodide on the phosphorescence efficiency led to heavy-atom enhancement factors ranging from 1.1 to 9.6, depending on the molecular structure and the pH conditions. 相似文献
933.
CO(2) as a separation switch for ionic liquid/organic mixtures 总被引:6,自引:0,他引:6
A novel technique to separate ionic liquids from organic compounds is introduced which uses carbon dioxide to induce the formation of an ionic liquid-rich phase and an organic-rich liquid phase in mixtures of methanol and 3-butyl-1-methyl-imidazolium hexafluorophosphate ([C4mim][PF6]). If the temperature is above the critical temperature of CO2 then the methanol-rich phase can become completely miscible with the CO2-rich phase, and this new phase is completely ionic liquid-free. Since CO2 is nonpolar, it is not equipped to solvate ions. As the CO2 dissolves in the methanol/[C4mim][PF6] mixture, the solvent power of the CO2-expanded liquid is significantly reduced, inducing the formation of the second liquid phase that is rich in ionic liquid. This presents a new way to recover products from ionic liquid mixtures and purify organic phases that have been contaminated with ionic liquid. Moreover, these results have important implications for reactions done in CO2/ionic liquid biphasic mixtures. 相似文献
934.
935.
John Koenitzer Bijan Khazai Jacob Hormadaly Robert Kershaw Kirby Dwight Aaron Wold 《Journal of solid state chemistry》1980,32(1):128-129
The orthorhombic α-PbO2 phase of FeNbO4 was prepared and its photoelectronic properties measured: Sintered disks were shown to be n type and gave a resistivity of 40 Ω-cm. Measurements of the photoresponse gave a flat-band potential between 0.1 and 0.4 V vs SCE at a pH of 8.5 and an optical band gap of 2.08(2) eV. Several higher-energy band gaps at 2.68(2), 2.94(2), 3.24(2), and 4.38(2) eV were also determined. There appears to be an enhancement of the quantum efficiency due to the presence of [FeO6] active centers while retaining the fundamental characteristics of the [NbO6] octahedra. 相似文献
936.
Maximilian Von Strandtmann Marvin P. Cohen John Shavel 《Journal of heterocyclic chemistry》1970,7(6):1311-1319
The reaction of o-phenolic Mannich bases with enamines yields cyclic O,N-acetals having a 2-aminodihydropyran or a spiropyranopiperidine structure in common. The 2-aminodihydro-pyrans are easily converted to 2-hydroxydihydropyrans and to pyrans. The preparation of a large variety of pyran-containing fused ring systems is reported. 相似文献
937.
Su S Acquilano DE Arumugasamy J Beeler AB Eastwood EL Giguere JR Lan P Lei X Min GK Yeager AR Zhou Y Panek JS Snyder JK Schaus SE Porco JA 《Organic letters》2005,7(13):2751-2754
[reaction: see text] The synthesis of a complex hybrid oxime library is reported utilizing convergent ligation of alkoxyamine and carbonyl monomers via "chemical domain shuffling". Initial biological screening of the library against human small cell lung carcinoma (A549) cells led to the identification of a novel hybrid dimer in contrast to the corresponding monomeric compounds which were found to be inactive. 相似文献
938.
We present exact analytical solutions for the much‐studied problem of a hydrogen‐like atom confined in a spherical box of radius R. These solutions, which are obtained for all states and all R, are expressed directly in terms of the Kummer M‐functions whose analytical and numerical properties are well known, and may be calculated using standard computing packages. The solutions are illustrated by precise calculations that yield accurate energies E for any given radius R, or for R when E is known. In the special case where E = 0, it is shown that the solution may be expressed in terms of Bessel functions. Finally, the physical assumptions made in applying this model to describe atomic confinement are discussed critically. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
939.
A complete series down group 6 of the formula M(NBu(t))(2)(dpma) has been synthesized, where dpma is N,N-di(pyrrolyl-alpha-methyl)-N-methylamine. A fourth complex, Mo(NAr)(2)(dpma) (4), was also prepared, where Ar is 2,6-diisopropylphenyl. All four of these complexes display geometries in the solid state best described as square pyramidal with one imido ligand occupying the axial position and the other an equatorial site. In all cases, the axial imido ligand has a significantly smaller M-N(imido)-C bond angle with respect to the equatorial multiple-bond substituent. From the (1)H, (13)C, and (14)N NMR spectra, the axial (bent) imido appears to be more electron-rich than the equatorial and linear imido, with the differences becoming less pronounced down the column. The angular deformation energies for the axial imido ligands were studied by DFT in order to discern if and to what extent imido bond angles were important energetically. The electronic energies associated with straightening the axial imido ligand, while holding the remainder of the molecule at the ground-state geometry, for the Cr, Mo, and W derivatives were calculated as 4.5, 2.7, and 2.0 kcal/mol, respectively. A straight-line plot is found for deformation energies versus estimated electronegativity of the group 6 metals in the +6 oxidation state. The study suggests that the electronic differences between metal imido ligands of different angles are quite small; however, the effects may be more pronounced for metal centers with higher electronegativity, e.g. Cr(VI) with electron-withdrawing ligands. 相似文献
940.
An immobilised whole cell catalyst SP361 has been shown to hydrolyse a range of 2-alkyl arylacetonitriles 1a–3a and amides 2b, 3b with good to excellent enantioselectivity. The absolute configuration of the derived amides and/or carboxylic acids shows remarkable changes according to the structure of the nitrite substrate. 相似文献