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The application of Schlieren and shadow techniques for the study of flame processes is discussed in relation to analytically useful premixed flames. The information obtained, particularly with shadowgraphs, may be correlated with the measured signals and signal noise in atomic-absorption and flame-emission spectrometry. 相似文献
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Graham LA Fout AR Kuehne KR White JL Mookherji B Marks FM Yap GP Zakharov LN Rheingold AL Rabinovich D 《Dalton transactions (Cambridge, England : 2003)》2005,(1):171-180
The manganese(I) tricarbonyl complexes (Bm(R))Mn(CO)3(R = Me, Bz, But, p-Tol) and (PhBmMe)Mn(CO)3, the first bis(mercaptoimidazolyl)borate derivatives for this metal, have been readily prepared and fully characterized. In particular, the presence of three-center-two-electron Mn...H-B interactions in these species, both in solution and in the solid state, has been investigated using a combination of IR and NMR spectroscopies and, in the case of the methyl-, tert-butyl- and para-tolyl-substituted derivatives, by X-ray crystallography. To complement these synthetic and structural studies, the tris(mercaptoimidazolyl)borate complexes (TmMe)Mn(CO)3(R = Me, Bz, But, p-Tol) and (PhTm(Me))Mn(CO)3, as well as the related pyrazolylbis(mercaptoimidazolyl)borate (pzBmMe)Mn(CO)3, have also been synthesized and characterized by a combination of analytical and spectroscopic techniques. 相似文献
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Pérez EM Dryden DT Leigh DA Teobaldi G Zerbetto F 《Journal of the American Chemical Society》2004,126(39):12210-12211
A novel type of mechanical switch is described in which light-induced translation of a macrocycle in a [2]rotaxane quenches anthracene fluorescence. Features of the system include the remarkable 200:1 difference in fluorescence intensity between the two positional states of the molecule ( approximately 85:1 between one isomer and the photostationary state). In principle the same concept could be used for mechanically switching virtually any property that can be influenced by functional group proximity effects. 相似文献
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Leigh DA Venturini A Wilson AJ Wong JK Zerbetto F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):4960-4969
Molecular modeling of four different reagent systems shows that the (free) energies of supramolecular interactions in the gas phase and in solution can explain the different reaction products (i.e., various sized macrocycles, catenanes, and linear oligomers) that are formed in classic amide-catenane-forming reactions. Self-assembly of the catenanes requires the formation of ordered intertwined chains and is driven by bifurcated hydrogen bonds, with pi stacking only playing a lesser role. The understanding gained from the computational study was used to predict the possibility of a new rotaxane-forming system that does not permit catenane formation. The predictions were confirmed by the successful synthesis and characterization (including X-ray crystallography) of two novel rotaxanes. 相似文献
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The first stimuli-responsive molecular shuttle that functions through reversible C-C bond formation is reported. 相似文献
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Charagundla SR Borthakur A Leigh JS Reddy R 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,162(1):113-121
Significant artifacts arise in T(1rho)-weighted imaging when nutation angles suffer small deviations from their expected values. These artifacts vary with spin-locking time and amplitude, severely limiting attempts to perform quantitative imaging or measurement of T(1rho) relaxation times. A theoretical model explaining the origin of these artifacts is presented in the context of a T(1rho)-prepared fast spin-echo imaging sequence. Experimentally obtained artifacts are compared to those predicted by theory and related to B(1) inhomogeneity. Finally, a "self-compensating" spin-locking preparatory pulse cluster is presented, in which the second half of the spin-locking pulse is phase-shifted by 180 degrees. Use of this pulse sequence maintains relatively uniform signal intensity despite large variations in flip angle, greatly reducing artifacts in T(1rho)-weighted imaging. 相似文献