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The rotational spectrum of 1,1-difluorobenzocyclopropene, measured in the X- and R-bands, has been analysed to give the rotational constants in the ground and first four vibrational states. These constants are in agreement with a structure based on those of crystallographically determined related molecules. Indirect evidence is adduced that the carbon skeleton is indeed planar. The dipole moment in the ground (3.572 ± 0.02 D) and first excited state (3.54 ± 0.03 D) has been determined through an analysis of the second-order Stark effect. This high value implies considerable polarisation of the π-electron framework. 相似文献
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Reference value standards, pH (RVS), for 0.05 mol kg?1 potassium hydrogenphthalate (KHPh) reference buffer solutions in 10, 30, 50 and 70% (w/w) 2-propanol/water solvent mixtures at temperatures from 288.15 to 318.15 K are determined from reversible e.m.f. measurements of the cell Pt¦H2¦KHPh + KCl¦AgCl¦Ag¦Pt. The consistency of the present results is confirmed by multilinear regression analysis of the pH values obtained for each solution composition and temperature, allowing appropriate interpolation of pH (RVS) values within the range of the experiment. The ancillary values of the standard e.m.f. of the cell Pt¦H2¦HCl¦AgCl¦Ag¦Pt are optimized through multilinear regression analysis of the available data in the literature, and the ancillary values of the first ionization constant of o-phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid) in these solvent mixtures are evaluated from reversible e.m.f. measurements of the cell Pt¦H2¦H2Ph + KHPh + KCl¦AgCl¦Ag¦Pt. 相似文献
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Dr. Caterina Bernacchioni Dr. Cecilia Pozzi Flavio Di Pisa Prof. Stefano Mangani Prof. Paola Turano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16213-16219
Ferritins are iron‐storage nanocage proteins that catalyze the oxidation of Fe2+ to Fe3+ at ferroxidase sites. By a combination of structural and spectroscopic techniques, Asp140, together with previously identified Glu57 and Glu136, is demonstrated to be an essential residue to promote the iron oxidation at the ferroxidase site. However, the presence of these three carboxylate moieties in close proximity to the catalytic centers is not essential to achieve binding of the Fe2+ substrate to the diferric ferroxidase sites with the same coordination geometries as in the wild‐type cages. 相似文献
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Computerized analytical instruments of late 70's and 80's are facing rapid technological obsolescence, although they are often retaining good analytical performances. Responsibility is to be attributed to the fast advance in computer technology, which is leaving little or no back-compatibility with old standards and data formats. Rejuvenation may be reached by simple hardware and software modifications, to allow data exchange with modern PC's and LIMS. Two typical case histories for spectrometric instrumentation of late 70's are then presented and discussed in a general fashion. 相似文献
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Fermo P Cariati F Pozzi A Tettamanti M Collina E Pitea D 《Fresenius' Journal of Analytical Chemistry》2000,366(3):267-272
The synergy of the micro FT-IR (Fourier Transform-Infrared) and SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-ray) techniques has been shown to be particularly helpful and effective for the characterization of inorganic compounds in fly ashes. The experimental data obtained by these techniques have been interpreted in comparison with those of other techniques. The presence of calcium carbonate, some sulfates, ammonium nitrate, calcium hydrogen phosphate, some chlorides, some oxides and aluminium silicates have been verified. 相似文献
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T. Di Matteo F. Pozzi T. Aste 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(1):3-11
Two kinds of filtered networks: minimum spanning trees (MSTs) and planar maximally filtered graphs (PMFGs) are constructed from dynamical correlations computed over a moving window. We study the evolution over time of both hierarchical and topological properties of these graphs in relation to market fluctuations. We verify that the dynamical PMFG preserves the same hierarchical structure as the dynamical MST, providing in addition a more significant and richer structure, a stronger robustness and dynamical stability. Central and peripheral stocks are differentiated by using a combination of different topological measures. We find stocks well connected and central; stocks well connected but peripheral; stocks poorly connected but central; stocks poorly connected and peripheral. It results that the Financial sector plays a central role in the entire system. The robustness, stability and persistence of these findings are verified by changing the time window and by performing the computations on different time periods. We discuss these results and the economic meaning of this hierarchical positioning. 相似文献
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[reaction: see text] A new poly(ethylene glycol)-supported porphyrin has been prepared and its ability as a promoter in photooxidation reactions has been studied. The PEG-supported catalyst exhibits high activity, comparable to that of a nonanchored sensitizer, and it is easily removable by filtration from the reaction mixture. The polymer-bound porphyrin has been recycled up to six times with no loss of chemical and stereochemical efficiency. 相似文献