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51.
The configuration-controlled regime and the diffusion-controlled regime of conformation-modulated fluorescence emission are systematically studied for Markovian and non-Markovian dynamics of the reaction coordinate. A path integral simulation is used to model fluorescence quenching processes on a semiflexible chain. First-order inhomogeneous cumulant expansion in the configuration-controlled regime defines a lower bound for the survival probability, while the Wilemski-Fixman approximation in the diffusion-controlled regime defines an upper bound. Inclusion of the experimental time window of the fluorescence measurement adds another dimension to the two kinetic regimes and provides a unified perspective for theoretical analysis and experimental investigation. We derive a rigorous generalization of the Wilemski-Fixman approximation [G. Wilemski and M. Fixman, J. Chem. Phys. 60, 866 (1974)] and recover the 1/D expansion of the average lifetime derived by Weiss [G. H. Weiss, J. Chem. Phys. 80, 2880 (1984)]. 相似文献
52.
Lingyan Zhang Ruo Yuan Xiaoqing Huang Yaqing Chai Shurui Cao 《Electrochemistry communications》2004,6(12):1222-1226
A novel potentiometric immunosensor for detection of Japanese B encephalitis vaccine was developed by immobilizing antiserum of Japanese B encephalitis on nano-Au/polymerized o-phenylenediamine (o-PDA) film on the platinum (Pt) electrode. The performance and factors influencing the performance of the resulting immunosensor were studied. The immunosensor showed a specific response to Japanese B encephalitis vaccine in the range 1.1 × 10−8 to 2.0 × 10−6 lgpfu/ml (plaque forming unit) with a detection limit of 6 × 10−9 lgpfu/ml. The correlation coefficient is 0.9986. The incubation time, incubation temperature, pH, reproducibility and stability of the immunosensor were also studied. The present work supplied a promising test method for biological products. 相似文献
53.
Xiao-Bai Sun Pei-Hua Zhao Yang-Jun Xu Li-Mei Sun Mei-Ai Cao Cheng-Shan Yuan 《Chemistry of Natural Compounds》2007,43(5):563-566
Investigation of the roots of Polygonum bistorta L. afforded seven compounds including five triterpenoids, a coumarin, and a steroid, the structures of which were identified
by EIMS, 1H NMR, 13C NMR, DEPT, and HMBC experiments. All the compounds have been isolated from Polygonum genus for the first time.
Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 463–465, September–October, 2007. 相似文献
54.
Here we report the formation and spectroscopic properties of cadmium sulfide (CdS) nanocrystal systems: individual nanocrystal and CdS aggregates. The optical absorption and luminescence spectra of the aggregated CdS nanocrystals and individual nanocrystal show exciton aggregate and individual exciton characteristics. Although it is not Bose-Einstein condensation, such aggregated quantum dots (QDs) seem to supply us opportunity to study the interactions and condensation of excitons in multi-QDs system, not in the separated QDs system. 相似文献
55.
The controlled synthesis of SrCO3 nanostructures with different morphologies, such as rodlike, whiskerlike, ellipsoidlike, and spherelike, were successfully achieved by the cationic surfactant-CTAB-microemulsion-mediated solvothermal method. Various comparison experiments showed that fundamental experimental parameters, such as the molar ratio of H2O to CTAB and the concentration of reactants, played important roles in the morphological control of SrCO3 nanostructures. A lower molar ratio of H2O to CTAB favors rodlike products, whereas a higher molar ratio generally leads to the formation of spherical products. A rational mechanism based on fusion, aggregate, and coalescence of microemulsion droplets is proposed for the selective formation of various morphologies. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and field-emission scanning electron microscope (FE-SEM) were used to characterize the products. 相似文献
56.
The explicit tau-leaping procedure attempts to speed up the stochastic simulation of a chemically reacting system by approximating the number of firings of each reaction channel during a chosen time increment tau as a Poisson random variable. Since the Poisson random variable can have arbitrarily large sample values, there is always the possibility that this procedure will cause one or more reaction channels to fire so many times during tau that the population of some reactant species will be driven negative. Two recent papers have shown how that unacceptable occurrence can be avoided by replacing the Poisson random variables with binomial random variables, whose values are naturally bounded. This paper describes a modified Poisson tau-leaping procedure that also avoids negative populations, but is easier to implement than the binomial procedure. The new Poisson procedure also introduces a second control parameter, whose value essentially dials the procedure from the original Poisson tau-leaping at one extreme to the exact stochastic simulation algorithm at the other; therefore, the modified Poisson procedure will generally be more accurate than the original Poisson procedure. 相似文献
57.
Photocatalytic oxidation of water is a promising method to realize large-scale H2O2 production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO2(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H2 and H2O2 production. Both H2 and H2O2 are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g–1 h–1 (first 1 h) for H2 and H2O2, respectively, which is much higher than that of a commercial Pt/TiO2(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H2O2, compared with the four-electron oxidation of water to O2. 相似文献
58.
Substituent effects on monoboronic acid sensors for saccharides based on N-phenyl-1,8-naphthalenedicarboximides 总被引:4,自引:0,他引:4
In the course of our investigations on new monoboronic acid saccharide sensors with C(0) spacers, a series of probes 1-6 based on 1,8-naphthalenedicarboximide were synthesized. Sensor 1 displays features typical of PET monoboronic acid sensors and shows high selectivity to fructose. Sensor 2 exhibits a novel dual emission and remarkable sensitivity for glucose relative to fructose and galactose through subtle changes in pH. Sensor 3 displays significantly enhanced fluorescence in the presence of galactose at low pH. Although probes 4-6 exhibit unique properties such as high quantum yield (Phi(F) = 0.407) and excellent solubility in water, they did not show significant change in fluorescence intensity in the presence of monosaccharides. The effects of substituent on all six probes lend support to the proposed photoelectrochemical model. 相似文献
59.
JPC – Journal of Planar Chromatography – Modern TLC - In this work we have studied the separation of a mixture of the sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron,... 相似文献
60.
Shen YH Li SH Li RT Han QB Zhao QS Liang L Sun HD Lu Y Cao P Zheng QT 《Organic letters》2004,6(10):1593-1595
Both coriatone (1). a novel highly oxygenated picrotoxane-type sesquiterpene, and corianlactone (2). with an unprecedented sesquiterpene basic skeleton, named coriane, were isolated from Coriaria nepalensis Wall. The structures of 1 and 2 were determined by analysis of their two-dimensional NMR data, and the structure of 2 was confirmed by X-ray analysis. Compounds 1 and 2 showed no remarkable inhibitory activity toward K(562) cells. They are cytotoxic with IC(50) > 50 microg/mL (cis-platinim: IC(50) = 0.49 microg/mL). 相似文献