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591.
Telmo L. C. Figueiredo Robert A. W. Johnstone Alexandra M. P. SantAna Sørensen Dominique Burget Patrice Jacques 《Photochemistry and photobiology》1999,69(5):517-528
Abstract— Fluorescence quantum yields and singlet lifetimes for a wide range of hydrophilic to hydrophobic porphyrins and metalloporphyrins have been determined in toluene, methanol or acetone. Photosensitized singlet oxygen yields have been determined in the same solvents. For some porphyrins, the same quantities were determined in an aqueous medium, through use of an amphiphilic polymer to solubilize the porphyrin sensitizer and target molecule, 1, 3-diphenylisobenzofuran. Because rate constants for the deactivation of singlet oxygen ( k d ) and for its reaction with a target molecule (k a ) are unknown in such aqueous polymer systems, a new method was developed for evaluating yields of singlet oxygen formation that also provides a value for the ratio kd /ka . A variation observed in quantum yield of singlet oxygen production for the aqueous polymer system with variation in initial concentration of the target molecule is discussed. 相似文献
592.
593.
Paul Müller Daniel Fernandez Patrice Nury Jean-Claude Rossier 《Helvetica chimica acta》1999,82(6):935-945
Olefins undergo cyclopropanation with diphenylsulfonium (ethoxycarbonyl)methylide (=diphenylsulfonium 2-ethoxy-2-oxoethylide; 3a ) in the presence of chiral CuI or RhII catalysts. trans/cis Ratios and ee's of the cyclopropanes 6 obtained with this ylide in the presence of a chiral CuI catalyst 7 are identical with those obtained with ethyl diazoacetate ( 4 ). In the case of catalysis with RhII, the trans/cis ratios of the cyclopropanes as well as the enantioselectivity change slightly upon going from the ylide 3a to diazoacetate 4 . 相似文献
594.
595.
The behaviour of stretched PVC fibres during thermomechanical treatments between 110–160°C has been studied. As far as shrinkage is concerned, three ranges of temperature have been characterized. Within the range 100–140°C the poly(vinyl chloride) undergoes a plastic deformation and has an elastoplastic behaviour. From 140 up to 170°C a creep phenomenon superimposes the elastic behaviour and then the polymer has a viscoplastic behaviour. As the temperature increases above 170°C there is flowing of polymer chains and the fibres break rapidly. Annealings carried out between 100 and 150°C cause the formation of ordered domains which are responsible for the formation of a temporary physical crosslinking network which hinders the shrinkage to such a temperature lower than their melting temperature. The loss of orientation of the amorphous phase is a rapid process which takes place as the temperature rises above 100°C even if the applied stress counterbalances the overall strain resulting from the potential shrinkage. 相似文献
596.
We characterize a system consisting of a two-mode waveguide coupled to a single-mode microring resonator possibly presenting a nonlinear response of Kerr type. By using the scattering parameter formalism extended to the multimode domain, we show that in the linear regime and for an ideally transparent medium, each resonance of the system can be exploited to perform complete even-to-odd (respectively, odd-to-even) modal conversion. Moreover, when the Kerr nonlinearity is effective, the microring enables a power-dependent modal switching mediated by phase bistability. Thanks to its mode-processing capabilities, this configuration is suitable to find application as a functional building-block in mode-division multiplexing (MDM) photonic integrated circuits. 相似文献
597.
Abidi Awatef Manaa Nessrin Mohamed Degani Estellé Patrice Borjini Mohammed Naceur 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12391-12408
Journal of Thermal Analysis and Calorimetry - A parametric numerical investigation has been performed of three-dimensional combined thermal–solutal capillary and buoyancy convection... 相似文献
598.
We developed a rapid and green synthesis of various isocyanurates by cyclotrimerization of isocyanates using TDAE (tetrakis(dimethylamino)ethylene). TDAE displays excellent performance in catalytic quantities, affording the corresponding trimer of isocyanates very rapidly, under air and at room temperature in good to excellent yields. 相似文献
599.
We propose a time domain decomposition method that breaks the sequentiality of the integration scheme for systems of ODE. Under the condition of differentiability of the flow, we transform the initial value problem into a well-posed boundary values problem using the symmetrization of the interval of time integration and time-reversible integration scheme. For systems of linear ODE, we explicitly construct the block tridiagonal system satisfied by the solutions at the time sub-intervals extremities. We then propose an iterative algorithm of Schwarz type for updating the interfaces conditions which can extend the method to systems of nonlinear ODE. 相似文献
600.
We report here the first example of an SRN1 reaction on propargylic chloride in heterocyclic series. The reaction of 4-(3-chloroprop-1-ynyl)-1,2-dimethyl-5-nitro-1H-imidazole with nitronate anions led to both the formation of the C-alkylated product through an SRN1 mechanism and the predominant ethylenic compound resulting from nitrous acid elimination on the C-alkylated product. Interestingly, in contrast to our previous works on SRN1 reactivity, no O-alkylated product was observed. 相似文献